Inflator system

ABSTRACT

Method for inflating an airbag in a vehicle to protect an occupant in the event of a crash involving the vehicle in which an inflator having a propellant is arranged in the vehicle, the propellant is ignited after determination of a crash involving the vehicle to generate gas therefrom, the gas is directed into an airbag and pressure in the airbag is controlled based on the occupant by varying the flow of gas into the airbag. Variation in the flow of gas into the airbag may be obtained by varying a flow of aspirating gas into a mixing chamber in which the aspirating gas mixes with gas generated from the propellant.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of:

-   -   1) U.S. patent application Ser. No. 10/043,557 filed Jan. 11,        2002, now U.S. Pat. No. 6,905,135 which is a        continuation-in-part of U.S. patent application Ser. No.        09/925,062 filed Aug. 8, 2001, now U.S. Pat. No. 6,733,036,        which is a continuation-in-part of U.S. patent application Ser.        No. 09/767,020 filed Jan. 23, 2001, now U.S. Pat. No. 6,533,316,        which is:        -   A) a continuation-in-part application of U.S. patent            application Ser. No. 09/073,403 filed May 6, 1998, now U.S.            Pat. No. 6,179,326, which is:            -   1) a continuation-in-part of U.S. patent application                Ser. No. 08/571,247 filed Dec. 12, 1995, now U.S. Pat.                No. 5,772,238; and            -   2) a continuation-in-part of U.S. patent application                Ser. No. 08/550,217 filed Oct. 30, 1995, now abandoned;                and        -   B) a continuation-in-part of U.S. patent application Ser.            No. 09/356,314 filed Jul. 16, 1999, now U.S. Pat. No.            6,326,704, which is:            -   1) a continuation-in-part of U.S. patent application                Ser. No. 08/947,661 filed Oct. 9, 1997, now abandoned                which claims priority under 35 U.S.C. §119(e) of U.S.                provisional patent application Ser. No. 60/028,046 filed                Oct. 10, 1996; and            -   2) a continuation-in-part of U.S. patent application                Ser. No. 09/137,918 filed Aug. 20, 1998, now U.S. Pat.                No. 6,175,787;    -   2) U.S. patent application Ser. No. 10/278,721 filed Oct. 23,        2002 claims priority under 35 U.S.C. §119(e) of U.S. provisional        patent application Ser. No. 60/348,720 filed Oct. 23, 2001;    -   3) U.S. patent application Ser. No. 10/638,743 filed Aug. 11,        2003 which is:        -   A) a continuation-in-part of U.S. patent application Ser.            No. 08/962,827 filed Nov. 3, 1997, now U.S. Pat. No.            6,609,903 which is a continuation-in-part of U.S. patent            application Ser. No. 08/476,076 filed Jun. 7, 1995, now U.S.            patent application Ser. No. 05/684,701;        -   B) a continuation-in-part of U.S. patent application Ser.            No. 10/331,060 filed Dec. 27, 2002 which is:            -   1) a continuation-in-part of U.S. patent application                Ser. No. 09/862,530 filed May 22, 2001, now U.S. Pat.                No. 6,557,889, which is:                -   a) a continuation-in-part of U.S. patent application                    Ser. No. 09/452,735 filed Dec. 1, 1999, now U.S.                    Pat. No. 6,234,519; and                -   b) a continuation-in-part of U.S. patent application                    Ser. No. 09/748,489 filed Dec. 26, 2000, now U.S.                    Pat. No. 6,328,126; and            -   2) a continuation-in-part of U.S. patent application                Ser. No. 08/865,525 filed May 29, 1997, now U.S. Pat.                No. 6,532,408;        -   C) a continuation-in-part of U.S. patent application Ser.            No. 09/435,045 filed Nov. 8, 1999, now U.S. Pat. No.            6,685,218, which is a continuation-in-part of U.S. patent            application Ser. No. 09/114,962 filed July 14, 1998, now            U.S. Pat. No. 6,419,265;        -   D) a continuation-in-part of U.S. patent application Ser.            No. 10/188,673 filed Jul. 3, 2002, now U.S. Pat. No.            6,738,697 which is a continuation-in-part of U.S. patent            application Ser. No. 09/753,186 filed Jan. 2, 2001, now U.S.            Pat. No. 6,484,080, which is a continuation-in-part of U.S.            patent application Ser. No. 09/137,918 filed Aug. 20, 1998,            now U.S. Pat. No. 6,175,787.        -   E) a continuation-in-part of U.S. patent application Ser.            No. 10/330,938 filed Dec. 27, 2002, now U.S. Pat. No.            6,823,244;    -   4) U.S. patent application Ser. No. 10/817,379 filed Apr. 2,        2004, now abandoned, which is:        -   A. a continuation-in-part of U.S. patent application Ser.            No. 09/888,575 filed Jun. 25, 2001, now U.S. Pat. No.            6,715,790, which is a continuation-in-part of U.S. patent            application Ser. No. 09/535,198, filed Mar. 27, 2000, now            U.S. Pat. No. 6,250,668, which is a continuation-in-part of            U.S. patent application Ser. No. 09/071,801, filed May 4,            1998, now U.S. Pat. No. 6,149,194, which is a            continuation-in-part of:            -   1) U.S. patent application Ser. No. 08/626,493, filed                Apr. 2, 1996, now U.S. Pat. No. 5,746,446, which is a                continuation-in-part of U.S. patent application Ser. No.                08/571,247, filed Dec. 12, 1995, now U.S. Pat. No.                5,772,238; and            -   2) U.S. patent application Ser. No. 08/795,418, filed                Feb. 4, 1997, now U.S. Pat. No. 5,863,068; and        -   B. a continuation-in part of U.S. patent application Ser.            No. 10/413,318 filed Apr. 14, 2003 now abandoned which            claims priority under 35 U.S.C. §119(e) of U.S. provisional            patent application Ser. No. 60/374,282 filed Apr. 19, 2002;            and    -   5) U.S. patent application Ser. No.10/974,919 filed Oct. 27,        2004 now U.S. Pat. No. 7,040,653.

This application is related to U.S. patent application Ser. No.08/247,763 filed May 23, 1994, now U.S. Pat. No. 5,505,485, and U.S.patent application Ser. No. 08/539,676, filed Oct. 5, 1995, now U.S.Pat. No. 5,653,464, all of which provide pertinent disclosure relativeto this specification and are incorporated by reference herein.

All of the above applications and patents, and any applications,publications and patents mentioned below, are incorporated herein byreference in their entirety and made a part hereof.

FIELD OF THE INVENTION

The present invention relates to methods and apparatus for sensing avehicle crash, such as a frontal crash, a side impact, a rear impact ora rollover, for the purpose of, for example, controlling an occupantprotection system.

The present invention also relates to steering wheel assemblies forvehicles and vehicles including the same and more particularly tosteering wheel assemblies which interact with an occupant protectionsystem to improve the deployment thereof.

The present invention also relates to a side curtain airbag system whichdeploys to prevent injury to vehicle occupants in a side impact orrollover accident.

The present invention also relates to airbags made from plastic filmsuch as a side curtain airbag arranged to deploy along the side of avehicle to protect occupants during a crash involving the vehicle,including a rollover. The side curtain airbag may even wrap around afront-seated occupant, i.e., have a frontal portion designed to deploybetween a front-seated occupant and the dashboard. Also there may be aplurality plastic film airbags that deploy in the event of a vehiclecrash. In some cases, such plastic film airbags may deploy to fillsubstantially all of the front passenger compartment of an automotive ortruck vehicle.

The present invention also relates to airbags having interconnectedcompartments for use in vehicular crashes whereby the airbags deploybefore or during the crash to cushion the occupant of the vehicle andprevent injury to the occupant. The present invention also relates to amethod for making an airbag having interconnected compartments and anoccupant protection system including an airbag with interconnectedcompartments.

The present invention also relates to vehicular airbags having a lowmass and made substantially from thin plastic film which are designed todeploy in a crash involving the vehicle so that if they impact thevehicle occupant wherever located, they will not cause significantinjury to the occupant. In order to make a film airbag of sufficientlylow mass so as not to injure the occupant, it has been recognized thatthe film airbag should be designed to arrest the propagation of a tearso that a small hole or break in the film does not result in acatastrophic failure, i.e., cause the airbag to burst like a balloon orotherwise prevent the airbag from deploying properly. One particularmethod of arresting the propagation of a tear of this invention is touse a combination of an elastomeric film and a reinforcement structurewhich in certain embodiments may be the elastomeric material itselfconstructed in a variable thickness pattern, i.e., have thinner andthicker sections, or in a manner so that it has strategically placedthicker sections, i.e., relative to remaining portions of the material,in view of stress considerations during deployment. Another particularmethod of arresting the propagation of a tear is to formulate theplastic film so that it exhibits the property of blunting, as describedbelow. One method of achieving this property is to laminate two or moreplastic films having different properties together. Typically, one ofthe films is more rigid and the other more elastic. One example is alamination comprising NYLON 6,6® and polyurethane films.

The present invention also relates to airbags including barrier coatingswhich provide reductions in gas, chemical and vapor permeability,especially side curtain airbags.

The present invention also relates to methods for manufacturing airbagmodules including an airbag having a barrier coating and an associatedinflator.

BACKGROUND OF THE INVENTION

The invention relates to several different areas and a discussion ofsome particular areas of interest follows. All mentioned patents,published patent applications and literature are incorporated byreference herein.

1. Crash Sensors

1.1 Pattern Recognition Approach to Crash Sensing

Pattern recognition techniques, such as artificial neural networks arefinding increased application in solving a variety of problems such asoptical character recognition, face recognition, voice recognition, andmilitary target identification. In the automotive industry inparticular, pattern recognition techniques are applied to identifyvarious objects within the passenger compartment of the vehicle, such asa rear facing child seat, as well as to identify threatening objectswith respect to the vehicle, such as an approaching vehicle about toimpact the side of the vehicle (see, e.g., U.S. Pat. Nos. 5,829,782,6,343,810 and U.S. RE37260).

Pattern recognition techniques are also applied to sense automobilecrashes for the purpose of determining whether or not to deploy anairbag or other passive restraint, or to tighten the seatbelts, cutoffthe fuel system, or unlock the doors after the crash (see, e.g., U.S.Pat. No. 5,684,701). In the past, pattern recognition techniques werenot applied to forecast the severity of automobile crashes for thepurpose of controlling the flow of gas into and/or out of an airbag totailor the airbag inflation characteristics and/or to control seatbeltretractors, pretensioners and energy dissipaters to match the crashseverity. Furthermore, such techniques were also not used to control theflow of gas into and/or out of an airbag to tailor the airbag inflationcharacteristics to the size, position and/or relative velocity of theoccupant or other factors such as seatbelt usage, seat and seat backpositions, headrest position, vehicle velocity, etc.

Neural networks are constructed of processing elements known as neuronsthat are interconnected using information channels often calledinterconnects organized into different layers. Each neuron can havemultiple inputs but generally only one output. Each output however isusually connected to all other neurons in the next layer in thedirection of processing. The neurons in the first layer operatecollectively on the input data as described in more detail below. Neuralnetworks learn by extracting relational information from the data andthe desired output. Neural networks have been applied to a wide varietyof pattern recognition problems including automobile occupant sensing,speech recognition, optical character recognition, and handwritinganalysis.

1.2 Electronic Crash Sensors

Electronic crash sensors currently used in sensing frontal impactstypically include accelerometers mounted in the passenger compartmentthat detect and measure vehicle accelerations during the crash. Theaccelerometer produces an analog signal proportional to the accelerationexperienced by the accelerometer and hence the vehicle on which it ismounted. An analog to digital converter (ADC) transforms this analogsignal into a digital time series. Crash sensor designers study thisdigital acceleration data and derive therefrom computer algorithms whichdetermine whether the acceleration data from a particular crash eventwarrants deployment of the airbag. This is usually a trial and errorprocess wherein the engineer or crash sensor designer observes data fromcrashes where the airbag is desired and when it is not needed, and otherevents, such as rough road and abusive incidents, where the airbag isnot needed. Finally, the engineer or crash sensor designer settles onthe “rules” for controlling deployment of the airbag which areprogrammed into an algorithm which seem to satisfy the requirements ofthe crash library, i.e., the crash data accumulated from numerouscrashes and other events and the associated desired restraint reaction.The resulting algorithm is not universal and most such engineers orcrash sensor designers will answer in the negative when asked whethertheir algorithm will work for all vehicles. Such an algorithm alsomerely determines that the airbag should or should not be triggered.Prior to the current assignee's activities, no attempt is believed tohave been made to ascertain or forecast the eventual severity of thecrash or, more specifically, to forecast the velocity change versus timeof the passenger compartment from the previous acceleration dataobtained from the accelerometer.

Several papers as listed below have been published pointing out some ofthe problems and limitations of electronic crash sensors mounted out ofthe crush zone of the vehicle, usually in a protected location in thepassenger compartment of the vehicle. These sensors are frequentlycalled single point crash sensors. Technical papers which discuss thelimitations of current single point sensors along with discussions ofthe theory of crash sensing are listed below. The only use of electronicsensors at the time of the filing of the current assignee's earliestparent patent application (U.S. Pat. No. 5,842,716 filed Sep. 16, 1993)was for non-crush zone sensing of frontal crashes. U.S. Pat. No.3,701,903 shows crash sensors mounted near the front of the vehicle butit also points out that they are used “ . . . in response to changes inthe vehicle's velocity” as opposed to the velocity change to a portionof the vehicle that undergoes crushing. Engineers involved in crashtesting at that time were aware that in a crash test, it was common tolose one or more of the front crush zone mounted accelerometers and thusthe prevailing wisdom was that the crush zone was not a place toposition electronic sensors.

These papers demonstrate, among other things, that there is no knowntheory that allows an engineer to develop an algorithm for sensingcrashes and selectively deploying the airbag except when the sensor islocated in the crush zone of the vehicle. These papers show that, ingeneral, there is insufficient information within the accelerationsignal measured in the passenger compartment to sense all crashes.Another conclusion suggested by these technical papers is that if analgorithm can be found which works for one vehicle, it will also workfor all vehicles since it is possible to create any crash pulse measuredin one vehicle, in any vehicle. In this regard, reference is made to SAEpaper 920124 discussed below.

In spite of the problems associated with finding the optimum crashsensor algorithm, many vehicles on the road today have electronic singlepoint crash sensors. Some of the problems associated with single pointsensors have the result that an out-of-position occupant who issufficiently close to the airbag at the time of deployment will likelybe injured or killed by the deployment itself. Fortunately, systems arenow being developed, and are in limited production, that monitor thelocation of occupants within the vehicle and can suppress deployment ofthe airbag if the occupant is more likely to be injured by thedeployment than by the accident. However, these systems are not believedto currently provide the information necessary for the control of airbagsystems, or the combination of seatbelt and airbag systems, which havethe capability of varying the flow of gas into and/or out of the airbagand thus to tailor the airbag to the size and/or weight of the occupant(and/or possibly another morphological characteristic of the occupant),as well as to the position, velocity and/or seatbelt use of theoccupant. More particularly, no such system is believed to have existed,prior to the conception by the current assignee's personnel, which usespattern recognition techniques to match the airbag deployment and/or gasdischarge from the airbag to the severity of the crash and/or the size,weight, position, velocity and/or seatbelt use of an occupant.

Once any crash sensor has determined that an airbag should be deployed,the system can perform other functions such as tightening the seatbeltsfor those vehicles which have seatbelt retractor systems, cutting off ofthe fuel system to prevent fuel spillage during or after the crash, andunlocking the doors after the crash to make it easier for theoccupant(s) to escape.

1.3 Crash Severity Prediction

When a crash commences, the vehicle starts decelerating and anaccelerometer located in the passenger compartment, and/or one or moresatellite or crush zone mounted accelerometers, begins sensing thisdeceleration and produces one or more electronic signals that vary overtime in proportion to the magnitude of the deceleration. These signalscontain information as to the type of the crash which can be used toidentify the crash. A crash into a pole gives a different signal than acrash into a rigid barrier, for example, even during the early portionof the crash before the airbag triggering decision has been made. Aneural network pattern recognition system can be trained to recognizeand identify the crash type from the early signal from a passengercompartment mounted sensor, for example, and further to forecast aheadthe velocity change versus time of the crash. If the neural network alsohas information from satellite or crush zone mounted sensors, theaccuracy of the forecast is significantly improved. Once this forecastis made, the severity and timing of the crash can be predicted. Thus,for a rigid barrier impact, an estimate of the eventual velocity changeof the crash can be made and the amount of gas needed in the airbag tocushion an occupant as well as the time available to direct that amountof gas into the airbag can be determined and used to control the airbaginflation.

Another example is a crash into a highway energy absorbing crashcushion. In this case, the neural-network-based sensor determines thatthis is a very slow crash and causes the airbag to inflate more slowlythereby reducing the incidence of collateral injuries such as brokenarms and eye lacerations.

In both of these cases, the entire decision making process takes placebefore the airbag deployment is initiated. In another situation where asoft crash is preceded by a hard crash, such as might happen if a polewere in front of a barrier, the neural network system would firstidentify the soft pole crash and begin slowly inflating the airbag.However, once the barrier impact begins, the system would recognize thatthe crash type has changed and recalculate the amount and timing of theintroduction of gas into the airbag and send appropriate commands to theinflation control system of the airbag to possibly vary the introductionof gas into the airbag. Again, if crush zone mounted sensors arepresent, the accuracy of the crash severity is greatly enhanced.

The use of pattern recognition techniques in crash sensors has anothersignificant advantage in that it can share the same pattern recognitionhardware and software with other systems in the vehicle. Patternrecognition techniques have proven effective in solving other problemsrelated to airbag passive restraints. In particular, the identificationof a rear-facing child seat located on the front passenger seat, so thatthe deployment of the airbag can be suppressed, has been demonstrated.Also, the use of pattern recognition techniques for the classificationof vehicles about to impact the subject vehicle, particularly the side,for use in anticipatory crash sensing shows great promise. Both of thesepattern recognition systems, as well as others under development, canuse the same computer system as the crash sensor and prediction systemof this invention. Moreover, both of these systems preferably will needto interact with, and should be part of, the diagnostic module used forfrontal impacts. It would be desirable for cost and reliabilityconsiderations, therefore, for all such systems to use the same computersystem or at least be located in the same electronic module. This isparticularly desirable since computers designed specially for solvingpattern recognition problems, such as neural-computers, are nowavailable and can be integrated into a custom application specificintegrated circuit (ASIC).

1.4 Crush Zone Mounted Sensors

In Society of Automotive Engineers (SAE) Paper No. 930650 entitled “AComplete Frontal Crash Sensor System”, the authors conclude that airbagcrash sensors mounted in the crush zone are necessary for proper sensingof airbag-required frontal crashes. They also conclude that such sensorsshould sense crashes to all portions of the front of the vehicle andthat sensors which sense the crush of the vehicle are preferred. Thetheory of crush sensing is presented in the above-referenced U.S.patents and patent applications and particularly in reference (6).

The tape switch and rod-in-tube crush sensors described in theabove-referenced U.S. patents and patent applications have performedsuccessfully on various staged vehicle frontal crashes into barriers andpoles. These sensors are generally not sufficient for sensing sideimpacts as discussed in reference (11), however, they can be successfulwhen used in conjunction with a passenger compartment mounted electronicsensor or as a safing sensor. Similarly, they are also being consideredwhen a deployable device, such as an airbag, is used for rear impacts.Newer elongate crush zone mounted sensors are being developed thatcontinuously measure the relative displacement, velocity change oracceleration of a particular location in the crush zone and thereforecan give much improved information about the locating of an impact andthe characteristics of the crash such as its severity.

Sensors have been widely used in the crush zone to sense and initiatedeployment of an air bag passive restraint system. These sensors includean air damped ball-in-tube sensor such as disclosed in U.S. Pat. Nos.3,974,350, 4,198,864, 4,284,863, 4,329,549 and 4,573,706 (all in thename of Breed) and a spring mass sensor such as disclosed in U.S. Pat.Nos. 4,116,132 and 4,167,276 (both in the name of Bell). In addition, apassenger compartment-mounted electronic sensor is now the most commonsensor in airbag systems. Each of these sensors has particularadvantages and shortcomings that are discussed in detail in U.S. Pat.No. 4,995,639.

The use of tape or ribbon switch technology as a crush switch was alsodisclosed in the '639 patent. Further research has shown that animprovement of this particular implementation has significant advantagesover some of the other implementations since the switch can be easilymade long and narrow and it can be made to respond to bending. In thefirst case, it can be designed to cover a significant distance acrossthe vehicle that increases the probability that it will be struck bycrushed material or bent as the crush zone propagates rearward in thevehicle during a crash. In the second case, it can be made small andlocated to sense the fact that one part of the vehicle has movedrelative to some other part or that the structure on which the sensor ismounted has deformed.

Other crush zone mounted crash sensors including crush switch designswhere the width and height dimensions are comparable, must either belarge and thus heavy, expensive and difficult to mount, or there is apossibility that the randomly shaped crushed material which forms theboundary of the crush zone will bridge the sensor resulting in latetriggering. This crushed material frequently contains holes, wrinkles orfolds or portions that may even be displaced or torn out during thecrash with the result that it is difficult to guarantee that aparticular small area where the sensor is mounted will be struck earlyin the crash.

A significant improvement results, therefore, if the sensor can stretchacross more of the vehicle or if it can determine that there has beenrelative motion or deformation of a portion of the vehicle on which thesensor is mounted. Some of the improved sensors described herein aresmall in height and thickness but can extend to whatever length isnecessary to achieve a high probability of a sensor triggering on timein a crash.

It has been found that conventional designs of tape or ribbon switcheshave the drawback that the force required to close the switch is verysmall compared with the forces which are normally present in automobilecrashes. During routine maintenance of the vehicle, the normal tapeswitch may be damaged or otherwise made to close and remain closed, withthe result that later, when the vehicle encounters a pot hole or othershock sufficient to cause the arming sensor to close, an inadvertent airbag deployment can result. Similarly, if the tape switch is mounted onthe front of the radiator support, which is a preferred mountinglocating for crush zone sensors, hail, heavy rain, stones or otherdebris from the road might impact the tape switch and cause a momentaryclosure or damage it. If this happens when the vehicle experiences ashock sufficient to cause the arming sensor to close, an inadvertent airbag deployment might also occur. The force typically required to close atape switch is less than one pound whereas tens of thousands of poundsare required to stop a vehicle in a crash and local forces greatly inexcess of 20 pounds are usually available to actuate a sensor during acrash.

The present invention seeks to eliminate these drawbacks through the useof a tape switch, rod-in-tube or coaxial cable design that requireseither a large force to actuate or a bending of the device due tostructural deformation as explained below.

In 1992, the current assignee published reference (5) where the authorsdemonstrate that there is insufficient information in the non-crush zoneof the vehicle to permit a decision to be made to deploy an airbag intime for many crashes. The crash sensors described herein and in thepatents and patent applications referenced above, provide an apparatusand method for determining that the crush zone of the automobile hasundergone a particular velocity change. This information can be used byitself to make the airbag deployment decision. As airbag systems becomemore sophisticated, however, the fact that the vehicle has undergone avelocity change in the crush zone can be used in conjunction with anelectronic sensor mounted in the passenger compartment to not onlydetermine that the airbag should be deployed but an assessment of theseverity of the crash can be made. In this case, the front crush zonemounted sensor of the type disclosed herein can be used as an input toan electronic algorithm and thereby permit a deployment strategy basedon the estimated severity of the accident. Although the sensorsdescribed herein are one preferred approach of providing thiscapability, the sensors disclosed in the above-referenced patents wouldalso be suitable. Alternately, in some cases, sensors of another designcan fulfill this function. Such sensors might be based on theelectromechanical technologies such as the ball-in-tube sensor describedin U.S. Pat. No. 4,900,880 and now electronic sensors can be used ascrush zone mounted sensors for this purpose as is the object of theinstant invention.

For the purposes herein, the crush zone is defined as that part of thevehicle which crushes or deforms during a particular crash. This is adifferent definition from that used elsewhere and in particular in theabove-referenced technical papers. Also for the purposes herein, theterminology Crush Sensing Zone, or CSZ, will be used to designate thatportion of the vehicle which is deformed or crushed during a crash atthe sensor-required trigger time. The sensor-required trigger time isconsidered the latest time that a crash sensor can trigger for there tobe sufficient time to deploy the airbag. This is determined by theairbag system designers and is a given parameter to the sensor designerfor a particular crash. There will be a different sensor-requiredtrigger time for each crash, however, it has been found, as reported inthe above references, that the CSZ is remarkably constant for allcrashes of the same type.

For example, the CSZ is nearly the same for all frontal barrier crashesregardless of the velocity of the crash. The same is true for 30 degreeangle barrier crashes although the CSZ is different here than forfrontal barrier crashes. Remarkably, and unexpectedly, it has also beenfound that when all frontal crashes at all different velocities aretaken into account, the CSZ rearmost boundary becomes an approximatethree dimensional surface lying mostly within the engine compartment ofthe vehicle, typically about ten to twelve inches behind the bumper atthe center, and extending backward when crashes outside of the rails areconsidered. Finally, if a sensor is placed on this CSZ surface so thatit is higher than the bumper level on the sides of the vehicle and lowerin the vehicle center, as shown in FIG. 7 herein, it will do aremarkable job at discriminating between airbag deployment required andnon-deployment crashes and still trigger by the sensor-required triggertime and before other sensors of comparable sensitivity. This system isnot perfect, however, it has been shown to do a better job than anyother sensor system now in use.

It was this discovery which provided a basis for the subject matterdescribed in U.S. Pat. No. 4,995,639 and then to the rod-in-tube sensordescribed in U.S. Pat. No. 5,441,301. During the process of implementingthe rod-in-tube sensor, it was found that the same theory applies torear impacts and that rod-in-tube sensors also have applicability toside impact sensing primarily as safing or arming sensors.

In U.S. Pat. No. 5,694,320, the theory of sensing rear impacts ispresented and it is concluded that an anticipatory sensing system ispreferred. This is because many people suffer whiplash injuries atrather low velocity impacts and if an inflatable restraint is used, therepair cost may be significant. To protect most people from whiplashinjuries in rear impacts, therefore, a resetable system is preferred.The argument on the other side is that if the headrest is properlypositioned, it will take care of all of the low velocity impacts and,therefore, an airbag can be used and reserved for the high velocityimpacts where a crush sensing crash sensor could be used. Rod-in-tubesensors disclosed herein are, therefore, ideal for use with a deployableheadrest mounted airbag for the same reasons that it is a good sensorfor sensing frontal impacts. Since the rear of a vehicle typically hasabout one third of the stiffness of the vehicle front, electronicsensors will have even a tougher time discriminating between trigger andnon-trigger cases for rear impacts. As disclosed in references 5 and 9,it is the soft crashes that are the most difficult for electronicsensors to sense in time.

Crush sensing crash sensors are not ideal for sensing side impactsalone, although at least one Volvo side impact system uses such asensing system. This is because the sensing time is so short that thereis virtually no crush (about two inches) at the time that the airbagmust be deployed. Since there is very little signal out of the crushzone where electronic sensors are mounted, electronic sensors alone arenot able to discriminate airbag required crashes from other crashes notrequiring airbag deployment. The combination of the two sensors, on theother hand, can be used to provide a reliable determination. The crushsensor determines that there has been two inches of crush and theelectronic sensor determines that the acceleration signal at that timeis consistent with an airbag-required crash occurring. Thus, althoughthey cannot be reliably used alone as a discriminating sensor for sideimpacts, the combined system does function properly. Recent advances nowpermit electronic crash sensors to be mounted in the side as well as thefront and rear crush zones.

An alternate use of the crush sensor such as the rod-in-tube sensor inside impacts is as a safing sensor. In this role, it merely determinesthat a crash is in progress and the main discriminating function ishandled by the velocity sensing sensors such as disclosed in U.S. Pat.No. 5,231,253.

Rod-in-tube or coaxial cable crush velocity sensing crash sensors solvethis side impact problem and thus applications include frontal, side andrear impacts, where in each case they enjoy significant advantages overall other crash sensing technologies. With respect to other relatedprior art, Peachey (U.S. Pat. No. 4,060,705) describes a pressureactuated continuous switch which designed to actuate about its entirecircumference, i.e., in all directions. The switch of the embodiment inFIG. 1 of Peachey includes a central, inner conductor, an insulatingthread helically wound around the conductor and an outer conductor, allhoused within a sheath of insulating material. The switch in theembodiment of FIG. 2 includes a central, inner conductor, an insulatingthread helically wound around the conductor, a sheath of graphite-loadedplastic surrounding the thread, an outer conductor surrounding thesheath and a sheath of insulating material surrounding the outerconductor. The switch in these embodiments is actuated when pressure isapplied to the switch so that the outer conductor (FIG. 1) or sheath(FIG. 2) is deflected to cause it to make contact with the innerconductor and thereby establish electrical contact between the inner andouter conductors in the embodiment of FIG. 2 through the sheath. In viewof the helical winding of the insulating thread around the innerconductor, these switches can be actuated by bending at almost alllocations (except for an impact into a location where the insulatingmaterial is interposed between the conductors).

U.S. Pat. No. 2,437,969 to Paul describes a deformable switch in theform of a tube that is actuatable at all circumferential points alongits length. The tube includes a central coil of electrically conductingwire, a braided electrically conducting, metal tube and insulatingseparators spaced at discrete locations along the length of the switchto support the tube around the wire. The switch is actuatable at allcircumferential locations along the length of the tube, except for thelocations at which the insulating separators 13 are located. In use,when pressure is applied to the tube, it deforms at the location atwhich pressure is applied thereby coming into contact with the wire andcausing a circuit to close.

U.S. Pat. No. 5,322,323 to Ohno et al. describes to a collision sensingsystem for an airbag including collision sensors and accelerationsensors wherein deployment of the airbag is based on a signal from thecollision sensors and an analysis of the output from the accelerationsensors.

U.S. Pat. No. 5,797,623 to Hubbard describes an allegedly unique sideimpact sensor based on a piezoelectric film. The sensor essentiallymeasures the energy of impact providing the entire force applied to thefilm, which would not in general be the case. The velocity of theimpacting vehicle can be determined again if the sensor absorbs theentire force and if the mass of the impacting object is known. Sinceneither of these can be assumed, the device will not provide ameasurement of the impacting velocity and therefore at best can act asan impact-sensing switch with some discriminating capability.

The prior art crush zone mounted sensors therefore are either forcesensing switches (Matsui) or piezoelectric film sensors (Hubbard)mounted in the forwardmost part of the crush zone, are velocity changesensors (ball-in-tube) mounted at the rear most edge of the CSZ or crushsensing switches also mounted at the rear most edge of the CSZ. Sensorsmounted at the rearmost edge of the CSZ by nature will trigger at thelast possible moment when the airbag must deploy based on the seatingposition of the average male occupant. It is known that currently up toabout 70% of vehicle occupants sit closer to the airbag than the averagemale and therefore such sensors trigger airbag deployment late for suchoccupants placing them at risk of being injured by the airbag.Previously, there are no velocity change sensors that are mounted in theforward part of the crush zone where the velocity change of the crashcan be determined early in the crash and the airbag deployed early.There is thus a need for such a crash sensor.

1.5 Side Impact Sensor Systems

Self-contained airbag systems contain all of the parts of the airbagsystem within a single package, in the case of mechanicalimplementations, and in the case of electrical or electronic systems,all parts except the primary source of electrical power and, in somecases, the diagnostic system. This includes the sensor, inflator andairbag. Potentially these systems have significant cost and reliabilityadvantages over conventional systems where the sensor(s), diagnostic andbackup power supply are mounted separate from the airbag module. Inmechanical implementations in particular, all of the wiring, thediagnostic system and backup power supply are eliminated. In spite ofthese advantages, self-contained airbag systems have only achievedlimited acceptance for frontal impacts and have so far not beenconsidered for side impacts.

The “all-mechanical” self-contained systems were the first to appear onthe market for frontal impacts but have not been widely adoptedpartially due to their sensitivity to accelerations in the vertical andlateral directions. These cross-axis accelerations have been shown toseriously degrade the performance of the most common all mechanicaldesign that is disclosed in Thuen, U.S. Pat. No. 4,580,810. Both frontaland side impact crashes frequently have severe cross-axis accelerations.

Additionally, all-mechanical self-contained airbag systems, such asdisclosed in the Thuen patent, require that the sensor be placed insideof the inflator which increases the strength requirements of theinflator walls and thus increases the size and weight of the system. Onesolution to this problem appears in Breed, U.S. Pat. No. 4,711,466, buthas not been implemented. This patent discloses a method of initiatingan inflator through the use of a percussion primer in combination with astab primer and the placement of the sensor outside of the inflator. Onedisadvantage of this system is that a hole must still be placed in theinflator wall to accommodate the percussion primer that has its ownhousing. This hole weakens the wall of the inflator and also provides apotential path for gas to escape.

Another disadvantage in the Thuen system that makes it unusable for sideimpacts, is that the arming system is sealed from the environment by anO-ring. This sealing method may perform satisfactorily when the moduleis mounted in the protected passenger compartment but it would not besatisfactory for side impact cases where the module would be mounted inthe vehicle door where it can be subjected to water, salt, dirt, andother harsh environments.

Self-contained electrical systems have also not been widely used. Whenairbags are used for both the driver and the passenger, self-containedairbag systems require a separate sensor and diagnostic for each module.In contrast to mechanical systems, the electronic sensor and diagnosticsystems used by most vehicle manufacturers are expensive. Thisduplication and associated cost required for electrical systemseliminates some of the advantages of the self-contained system.

Sensors located in the passenger compartment of a vehicle can catch mostairbag-required crashes for frontal impacts, particularly if theoccupants are wearing seatbelts. However, researchers now believe thatthere are a significant number of crashes which cannot be sensed in timein the passenger compartment and that this will require the addition ofanother sensor mounted in the crush zone (see, e.g., reference 5). Iftrue, this will eventually eliminate the use of self-contained airbagsystems for frontal impacts.

Some of these problems do not apply to side impacts mainly because sideimpact sensors must trigger in a very few milliseconds when there is nosignificant signal at any point in the vehicle except where the car iscrushing or at locations rigidly attached to this crush zone. Eachairbag system must be mounted in the crush zone and generally will haveits own sensor. Self-contained airbag systems have not been usedpreviously for occupant protection for side impacts which is largely dueto the misconception that side impact sensing requires the use ofelongated switches as is discussed in detail in U.S. Pat. No. 5,231,253.These elongated prior art side impact crush-sensing switches are notreadily adaptable to the more compact self-contained designs. Therealization that a moving mass sensor was the proper method for sensingside impacts has now led to the development of the side impactself-contained airbag system of this invention. The theory of sensingside impacts is included in the '253 patent.

In electro-mechanical and electronic self-contained modules, the backuppower supply and diagnostic system are frequently mounted apart from theairbag system. If a wire is severed during a crash but before the airbagdeploys, the system may lose its power and fail to deploy. This is morelikely to happen in a side impact where the wires must travel inside ofthe door. For this reason, mechanical self-contained systems have asignificant reliability advantage over conventional electrical systems.

Finally, the space available for the mounting of airbag systems in thedoors of vehicles is frequently severely limited making it desirablethat the airbag module be as small as possible. Conventional gasgenerators use sodium azide as the gas generating propellant. Thisrequires that the gas be cooled and extensively filtered to remove thesodium oxide, a toxic product of combustion. This is because the gas isexhausted into the passenger compartment where it can burn an occupantand is inhaled. If the gas is not permitted to enter the passengercompartment, the temperature of the gas can be higher and the productsof combustion can contain toxic chemicals, such as carbon dioxide.

These and other problems associated with self-contained airbag systemsand side impact sensors are solved by inventions disclosed herein.

1.6 Anticipatory Sensing

Although there has been a great deal of discussion on the use ofanticipatory sensors for initiating restraint deployment, no practicalsystems have been developed other than those of the current assignee.The basic problem has been that an airbag should not be deployed unlessthe approaching object can be identified as a serious threat. The neuralnetwork systems developed by the current assignee is the first systemcapable of identifying such threatening objects.

1.7 Rollover Sensing

Various sensors exist for rollover sensing which detect the angularposition of the vehicle.

1.8 Rear Impact Sensing

Various sensors exist for rear impact sensing which detect an impactinto the rear of the vehicle.

1.9 Sensor Combinations

Up until the time that the first parent application was filed on thisinvention, it is believed that the only use of sensor combinations waswhere a discriminating sensor was in series with a safing or armingsensor and where a crush zone mounted discriminating sensor was inparallel with a passenger compartment discriminating sensor where eitherone could initiate deployment of the restraint system.

1.10 Safety Bus

It is not uncommon for an automotive vehicle today to have many motors,other actuators, lights etc., controlled by one hundred or more switchesand fifty or more relays and connected together by almost five hundredmeters of wire, and close to one thousand pin connections grouped invarious numbers into connectors. It is not surprising therefore that theelectrical system in a vehicle is by far the most unreliable system ofthe vehicle and the probable cause of most warranty repairs.

Unfortunately, the automobile industry is taking a piecemeal approach tosolving this problem when a revolutionary approach is called for.Indeed, the current trend in the automotive industry is to group severaldevices of the vehicle's electrical system together which are locatedgeometrically or physically in the same area of the vehicle and connectthem to a zone module which is then connected by communication and powerbuses to the remainder of the vehicle's electrical system. The resultinghybrid systems still contain substantially the same number andassortment of connectors with only about a 20% reduction in the amountof wire in the vehicle.

Finally, the airbag electronics are generally housed separate and apartfrom the airbag module and the energy needed to initiate the inflator istransmitted to the airbag module after the crash sensor has determinedthat the airbag deployment is required. This has resulted in manyfailures of the airbag system due to shorted wires and other relatedcauses. These and other problems could be solved if the crash sensorelectronics send a coded signal to the airbag module and the electronicsassociated with the module decoded the signal to initiate the inflator.

The diagnostics circuitry can then also be part of or associated withthe module along with the backup power supply which now also becomes theprimary power supply for the module. This is sometimes known as thesafety bus and there appears to be no prior art to the assignee'spatents.

2. Inflators

2.1 Elongate Airbag Module

2.1.1 Ceiling Mounted

Devices are now being offered on vehicles that will monitor the positionof the occupant and prevent the airbag from deploying if the occupant isdangerously close to the module where he or she can be seriously injuredby the deployment. Some systems will also prevent deployment if the seatin connection with which the airbag operates is unoccupied. An alternateapproach is to move the deployment doors to a location away from normaloccupant positions. One such location is the ceiling of the vehicle. Oneproblem with ceiling-mounted airbags is that the distance required forthe airbag to travel, in some cases, is longer and therefore a largerairbag is needed with greater deployment time. With the use of lightairbag materials, such as thin plastic film, as disclosed in U.S. Pat.Nos. 5,505,485 and 5,653,464, and the use of more efficient inflators,both of these problems can be solved especially for the front and rearseat passengers. The driver poses a different problem since it would bedifficult to position a ceiling-mounted airbag module where the airbagwould always be projected properly between the occupant and the steeringwheel. On the other hand, the driver can usually ride down on thesteering wheel if he or she is initially positioned close to it.

2.1.2 Steer by Wire

This problem for the driver's airbag system is not the concept ofmounting the airbag on the ceiling, but the design of the steering wheeland steering column. These designs come from the time when the only wayof steering an automobile was through mechanical linkages. The majorityof vehicles manufactured today have power-assisted steering systems and,in fact, most drivers would have difficulty steering a car today if thepower steering failed. If servo power steering were used, the need for amechanical linkage between a steering wheel, or other such device, andthe power steering system would no longer be necessary. Servo powersteering for the purposes here will mean those cases where the linkagebetween the manually operated steering device, which regardless of whatthat device is, will herein be called a steering wheel, is done with aservo system either electrically or hydraulically and the system doesnot have an operative mechanical connection between the steering wheeland the steering mechanism which moves the wheels.

The problem of educating the general population, which has become securein the feeling of a steering wheel and steering column, might beinsurmountable if it were not for the substantial safety advantageresulting from substituting servo power steering for conventionalsteering systems and using a non-steering wheel mounted airbag modulefor the driver.

The steering wheel and steering column are among the most dangerousparts of the vehicle to the occupant. Small people, for example, who arewearing seatbelts can still be seriously injured or killed in accidentsas their faces slam into steering wheel hubs. The problem of properlypositioning an airbag, when the comfort and convenience features oftelescoping and tilting steering columns are considered, results insubstantial safety compromises. Deployment-induced injuries which resultwhen a small person is close to the steering wheel when the airbagdeploys have already caused several deaths and numerous seriousinjuries. Future vehicles, therefore, for safety reasons should beconstructed without the massive steering wheel and steering column andsubstitute therefor a servo steering assembly. With this modification, aceiling-mounted airbag module, such as discussed herein, becomesfeasible for the driver as well as the other seating positions in thevehicle.

The front seat of the vehicle often has an airbag for the passenger andanother for the driver. In some accidents, an occupant, and particularlya center-seated occupant, can pass between the two airbags and notreceive the full protection from either one. If a ceiling-mounted airbagsystem were used, a single airbag could be deployed to cover the entirefront seat greatly simplifying the airbag system design.

2.1.3 Mounted Rear-of-Seat

Other than disclosed in patents to the assignee, there appears not to beany prior art for rear of seat mounted airbags.

2.2 Aspirated Inflators

There are airbag modules in use which are relatively large, heavy,expensive and inefficient. As a result, airbags are now primarily onlyused for protecting the passenger and driver in a frontal impact,although most automobile manufacturers currently offer a small airbagproviding limited protection in side impacts and many are now offeringhead protection or curtain airbags. The main advantage of airbags overother energy absorbing structures is that they utilize the space betweenthe occupant and vehicle interior surfaces to absorb the kinetic energyof the occupant during a crash, cushioning the impending impact of theoccupant with the vehicle interior surfaces. Airbags have been sosuccessful in frontal impacts that it is only a matter of time beforethey are effectively used for side impact protection in all vehicles,protection for rear seat occupants and in place of current kneebolsters. Substantial improvements, however, must be made in airbagsbefore they assume many of these additional tasks.

A good place to start describing the problems with current airbags iswith a calculation of the amount of energy used in a typical airbaginflator and how much energy is required to inflate an airbag. By oneanalysis, the chemical propellant in a typical driver's side inflatorcontains approximately 50,000 foot pounds (68,000 joules) of energy. Acalculation made to determine the energy required to inflate a driver'sside airbag yields an estimate of about 500 foot pounds (680 joules). Acomparison of these numbers shows that approximately 99% of the energyin a chemical propellant is lost, that is, generated but not needed forinflation of the airbag. One reason for this is that there is a mismatchbetween the output of a burning propellant and the inflationrequirements of an airbag. In engineering this is known as an impedancemismatch. Stated simply, propellants naturally produce gases having hightemperatures and high pressures and low gas flow rates. Airbags, on theother hand, need gases with low temperatures and low pressures and highgas flow rates.

In view of this impedance mismatch, inflators are, in theory at least,many times larger then they would have to be if the energy of thepropellant contained within the inflator were efficiently utilized. Someattempts to partially solve this problem have resulted in a so-called“hybrid” inflator where a stored pressurized gas is heated by apropellant to inflate the airbag. Such systems are considerably moreenergy efficient, however, they also require a container of highpressure gas and monitoring of the pressure in that container. Othersystems have attempted to use aspiration techniques, but because of thegeometry constraints of current car inflator designs and mountinglocations, and for other reasons, currently used aspiration systems areonly able to draw significantly less than 30% of the gas needed toinflate an airbag from the passenger compartment. Theoretical studiesand recent experiments have shown that as much as 90% or more of the gascould be obtained in this manner.

Furthermore, since inflators are large and inefficient, severerestrictions have been placed on the type of propellants that can beused since the combustion products of the propellant must be breathableby automobile occupants. It is of little value to save an occupant fromdeath in an automobile accident only to suffocate him from an excessiveamount of carbon dioxide in the air within the passenger compartmentafter the accident. If inflators operated more efficiently, thenalternate, more efficient but slightly toxic propellants could be used.Also, most current inflators are made from propellants, namely sodiumaside, which are not totally consumed. Only about 40% of the mass ofsodium azide propellants currently being used, for example, enters theairbag as gas. This residual mass is very hot and requires the inflatorto be mounted away from combustible materials further adding to the massand size of the airbag system and restricts the materials that can beused for the inflator.

It is a persistent problem in the art that many people are beingseriously injured or even killed today by the airbag itself. Thisgenerally happens when an occupant is out-of-position and against anairbag module when the airbag deploys. In order to open the modulecover, sometimes called the deployment door, substantial pressure mustfirst build up in the airbag before enough force is generated to burstopen the cover. This pressure is even greater if the occupant is in aposition that prevents the door from opening. As a result, work isunderway to substantially reduce the amount of energy required to openthe deployment doors and devices have been developed which pop off thedeployment door or else cut the deployment door material usingpyrotechnics, for example.

One reason that this is such a significant problem is that the airbagmodule itself is quite large and, in particular, the airbags are madeout of thick, heavy material and packaged in a poor, folded geometry.The airbag, for example, which protects the passenger is housed in amodule which is typically about one third as long as the deployedairbag. All of this heavy airbag material must be rolled and foldedinside this comparatively small module, thus requiring substantialenergy to unfold during deployment. This situation could besubstantially improved if the airbag module were to have an alternategeometry and if the airbag material were substantially lighter andthinner and, therefore, less massive and folded mainly parallel to theinflator. Even the time to deploy the airbag is substantially affectedby the mass of the airbag material and the need to unfold an airbag witha complicated folding pattern. Parallel folding, as used herein, meansthat the airbag material is folded with the fold lines substantiallyparallel to the axis of the inflator without being folded overlengthwise as is now done with conventional airbag folding patterns.

One method of partially solving many of these problems is to use anefficient aspirated airbag system. There have been numerous patentsgranted on designs for airbag systems using aspirated inflators. Inthese patents as well as in the discussion herein the term “pumpingratio” is used. The pumping ratio as used in the art is defined as theratio of the mass of gas aspirated from the environment, either frominside or outside of the vehicle, to the mass of gas generated byburning the propellant. An alternate definition is the ratio of thetotal gas in the airbag to the gas produced by the propellant. A briefdescription of several pertinent aspiration patents follows:

U.S. Pat. No. 2,052,869 to Coanda shows the manner in which a fluid jetis caused to change direction, although no mention is made of its use inairbags. This principle, the “Coanda effect”, is used in someimplementations of the instant invention as well as in U.S. Pat. No.3,909,037 to Stewart discussed below. Its primary contribution is thatwhen used in inflator designs, it permits a reduction in the length ofthe nozzle required to efficiently aspirate air into the airbag. Nodisclosure is made of a pumping ratio in this system and in fact it isnot an object of Coanda to aspirate fluid.

U.S. Pat. No. 3,204,862 to Hadeler predates vehicular airbags but isnonetheless a good example of the use of aspiration to inflate aninflatable structure. In this device, an inflating gas is injected intoan annular converging-diverging nozzle and some space efficiency isobtained by locating the nozzle so that the flow is parallel to the wallof the inflatable structure. No mention is made of a pumping ratio ofthis device and furthermore, this device is circular.

U.S. Pat. No. 3,632,133 to Hass provides a good example of a nozzle in acircular module with a high pumping ratio in an early construction of anairbag. Although analysis indicates that pumping ratios of 4:1 or 5:1would be difficult to achieve with this design as illustrated,nevertheless, this reference illustrates the size and rough shape of anaspirating system which is required to obtain high pumping ratios usingthe prior art designs.

U.S. Pat. No. 3,909,037 to Stewart provides a good example of theapplication of the Coanda effect to airbag aspirating inflators.Stewart, nevertheless, still discards most of the energy in thepropellant which is absorbed as heat in the inflator mechanism. Mostpropellants considered for airbag applications burn at pressures inexcess of about 1000 psig. Stewart discloses that the maximum efficiencycorresponding to a 5:1 pumping ratio occurs at inflator gas pressures ofabout 5-45 psig. In order to reduce the pressure, Stewart utilizes acomplicated filtering system similar to that used in conventionalinflators. Stewart requires the use of valves to close off theaspiration ports when the system is not aspirating. Through the use ofthe Coanda effect, Stewart alludes to a substantial reduction in thesize of the aspiration system, compared to Hass for example. Also,Stewart shows only a simple converging nozzle through which the burningpropellant is passed.

U.S. Pat. No. 4,833,996 to Hayashi et al. describes a gas generatingapparatus for inflating an airbag which is circular and allegedlyprovides an instantaneous pumping ratio of up to 7:1 although analysisshows that this is unlikely in the illustrated geometry. The averagepumping ratio is specified to be up to 4:1. This invention is designedfor the driver side of the vehicle where unrestricted access to theaspirating port might be difficult to achieve when mounted on a steeringwheel. The propellant of choice in Hayashi et al. is sodium azide whichrequires extensive filtering to remove particulates. No attempt has beenmade in this design to optimize the nozzle geometry to make use of aconverging-diverging nozzle design, for example. Also, the inflator hasa roughly conventional driver side shape. It is also interesting to notethat no mention is made of valves to close off or restrict flow throughthe aspiration port during deflation. Since most aspiration designshaving even substantially smaller pumping ratios provide for suchvalves, the elimination of these valves would be a significant advancein the art. Analysis shows, however, that the opening needed for theclaimed aspiration ratios would in general be far too large for it alsoto be used for exhausting the airbag during a crash.

U.S. Pat. No. 4,877,264 to Cuevas describes an aspirating/venting airbagmodule assembly which includes a circular gas generator and contemplatesthe use of conventional sodium aside propellants or equivalent. Theaspiration or pumping ratio of this inflator is approximately 0.2:1,substantially below that of Hayashi et al., but more in line withaspiration systems in common use today. This design also does notrequire use of aspiration valves which is more reasonable for this case,but still unlikely, since the aspiration port area is much smaller. Noattempt has been made to optimize the nozzle design as is evident by theshort nozzle length and the low pumping ratio.

U.S. Pat. No. 4,909,549 to Poole et al. describes a process forinflating an airbag with an aspiration system but does not discuss theaspiration design or mechanism and merely asserts that a ratio as highas 4:1 is possible but assumes that 2.5:1 is available. This patent issignificant in that it discloses the idea that if such high pumpingratios are obtainable (i.e., 2.5:1 compared with 0.2:1 for inflators inuse), then certain propellants, which would otherwise be unacceptabledue to their production of toxic chemicals, can be used. For example,the patent discloses the use of tetrazol compounds. It is interesting tonote that there as yet is no commercialization of the Poole et al.invention which raises the question as to whether such high aspirationratios are in fact achievable with any of the prior art designs.Analysis has shown that this is the case, that is, that such largeaspiration ratios are not achievable with the prior art designs.

U.S. Pat. No. 4,928,991 to Thom describes an aspirating inflatorassembly including aspiration valves which are generally needed in allhigh pumping ratio aspiration systems. Sodium azide is the propellantused. Pumping ratios of 1:1 to 1.5:1 are mentioned in this patent whichby analysis is possible. It is noteworthy that the preamble of thispatent discloses that the state of the art of aspirating inflatorsyields pumping ratios of 0.1:1 to 0.5:1, far below those specified inseveral of the above referenced earlier patents. Little attempt has beenmade to optimize the nozzle design.

U.S. Pat. No. 5,004,586 to Hayashi et al. describes a sodium azidedriver side inflator in which the aspirating air flows through a seriesof annular slots on the circumference of the circular inflator incontrast to the earlier Hayashi et al. patent where the flow was on theaxis. Similar pumping ratios of about 4:1 are claimed however, which byanalysis is unlikely. Once again, aspiration valves are not shown andthe reason that they can be neglected is not discussed. An inefficientnozzle design is again illustrated. The lack of commercial success ofthese two Hayashi patents is probably due to the fact that such highpumping ratios as claimed are not in fact achievable in the geometriesillustrated.

U.S. Pat. No. 5,060,973 to Giovanetti describes a liquid propellantairbag gas generator wherein the propellant burns clean and does notrequire filters to trap solid particles. Thus, it is one preferredpropellant for use in the instant invention. This system howeverproduces a gas which is too hot for use directly to inflate an airbag.The gas also contains substantial quantities of steam as well as carbondioxide. The steam can cause burns to occupants and carbon dioxide insignificant quantities is toxic. The gas generator is also circular.Aspirating systems are therefore required when using the liquidpropellant disclosed in this patent, or alternately, the gas generatedmust be exhausted outside of the vehicle.

U.S. Pat. No. 5,129,674 to Levosinski describes a converging-divergingnozzle design which provides for more efficient aspiration than some ofthe above discussed patents. Nevertheless, the airbag system disclosedis quite large and limited in length such that the flow passageways arequite large which requires a long nozzle design for efficient operation.Since there is insufficient space for a long nozzle, it can be estimatedthat this system has a pumping ratio less than 1:1 and probably lessthan 0.2:1. Once again, a sodium azide based propellant is used.

U.S. Pat. No. 5,207,450 to Pack, Jr. et al. describes an aspirated aircushion restraint system in which no attempt was made to optimize thenozzle design for this sodium azide driver side airbag. Also, aspirationvalves are used although it is suggested that the exhaust from theairbag can be made through the aspirating holes thereby eliminating theneed for the flapper valves. No analysis, however, is provided to provethat the area of the aspiration holes is comparable to the area of theexhaust holes normally provided in the airbag. Although no mention ismade of the pumping ratio of this design, the device as illustratedappears to be approximately the same size as a conventional driver sideinflator. This, coupled with an analysis of the geometry, indicates apumping ratio of less than 1:1 and probably less than 0.2:1. Thestatement that the aspiration valves are not needed also indicates thatthe aspiration ratio must be small. Large inlet ports which are neededfor large aspiration ratios are generally much larger than the typicalairbag exhaust ports.

U.S. Pat. No. 5,286,054 to Cuevas describes an aspirating/venting motorvehicle passenger airbag module in which the principal of operation issimilar to the '264 patent discussed above. The aspiration pumping ratioof this device is 0.15:1 to 0.2:1 which is in line with conventionalaspirated inflators. It is interesting to note that this pioneer in thefield does not avail himself of designs purporting to yield higherpumping ratios. The nozzle design has not been optimized.

U.S. Pat. No. 6,062,143 to Grace et al. describes a distributed chargeinflator system including a distributed gas-generating material having afaster burning center core ignition material surrounded by supplementalpropellant, and an initiator to ignite the gas generating material upona signal from an initiating device. A homogeneous mixture of ignitionmaterial and propellant is also described.

Other U.S. patents which are relevant to the instant invention but whichwill not be discussed in detail are: U.S. Pat. No. 3,158,314 to Young etal., U.S. Pat. No. 3,370,784 to Day, U.S. Pat. No. 5,085,465 to Hieahim,U.S. Pat. No. 5,100,172 to Van Voorhies et al., U.S. Pat. No. 5,193,847to Nakayama, U.S. Pat. No. 5,332,259 to Conlee et al. and U.S. Pat. No.5,423,571 to Hawthorn.

None of the prior art inflators are believed to contain the advantagesof the combination of (i) a linear inflator having a small cross sectionthereby permitting an efficient nozzle design wherein the length of thenozzle is much greater than the aspiration port opening, (ii) a nonsodium aside propellant which may produce toxic gas if not diluted withsubstantial quantities of ambient air, and (iii) an inflator whereminimal or no filtering or heat absorption is required.

It is interesting to note that in spite of the large aspiration pumpingratios mentioned and even claimed in the prior art mentioned above, andto the very significant advantages which would result if such ratioscould be achieved, none has been successfully adapted to an automobileairbag system. One reason may be that pumping ratios which areachievable in a steady state laboratory environment are more difficultto achieve in the transient conditions of an actual airbag deployment.

None of these prior art designs has resulted in a thin linear modulewhich permits the space necessary for an efficient nozzle design asdisclosed herein. In spite of the many advantages claimed in the priorart patents, none have resulted in a module which can be mounted withinthe vehicle headliner trim, for example, or can be made to conform to acurved surface. In fact, the rigid shape of conventional airbag moduleshas forced the vehicle interior designers to compromise their designssince the surface of such modules must be a substantially flat plane.

With respect to airbag systems including a plurality of inflatableairbags or unconventionally large airbags and inflators therefor,automobile manufacturers are now installing more than two airbags into avehicle. The placement of both side and rear seat airbags have in facttaken place. Nissan for example has installed some rear airbags. Mostautomobile manufacturers are now installing side airbags. However,Nissan has stated that it cannot provide more than a total of twoairbags in the vehicle and that it will not offer a front passenger sideairbag for those vehicles that have a rear seat airbag. Side airbagswill generally not deploy when the frontal airbags do because if morethan two airbags would be deployed in a vehicle at the same time, thepressure generated by the deploying airbags within the passengercompartment of the vehicle creates large forces on the doors. Theseforces may be sufficient to force the doors open and consequently, ifthe doors of the vehicle are forced open during a crash, vehicleoccupants might be ejected, greatly increasing the likelihood of seriousinjury. In addition, the pressure generated within the passengercompartment creates excessive noise which can injure human beings.

In addition to airbags for side impacts and rear seats, it is likelythat airbags will be used as knee bolsters since automobilemanufacturers are having serious problems protecting knees from injuryin crashes while providing the comfort space desired by their customers.

As soon as three or more non-aspirated airbags are deployed in anaccident, provisions should be made to open a hole in the vehicle topermit the pressure generated by the deploying airbags to escape. Whathas not been appreciated, however, is that once there is a significantopening from the vehicle to the outside, the requirements for thecomposition of the inflator gases used to inflate the airbags change andinflators which generate a significant amount of toxic gas becomefeasible, as will be discussed below.

The primary gas generating propellant used in airbag systems is sodiumaside. This is partially due to the fact that when sodium aside burns,in the presence of an oxidizer, it produces large amounts of Nitrogengas. It also produces sodium oxide which must be retained in theinflator since sodium oxide, when mixed with moisture, becomes lye andis very toxic to humans. Thus, current inflators emit only nitrogen gasinto the passenger compartment which occupants can breath for a longperiod of time in a closed passenger compartment without danger. Thesodium azide inflators also are large to accommodate the fact that about60% of the gas generating material remains in the inflator with onlyabout 40% emerging as gas.

Other propellants, including nitrocellulose, nitroguanidine, and otherdouble base and triple base formulations, as well as a large number ofliquid propellants, exist which could be used to inflate airbags,however they usually produce various quantities of gases containingcompounds of nitrogen and oxygen plus significant amounts of carbondioxide. In many cases, the gases produced by these other propellantsare only toxic to humans if breathed over an extended period of time. Ifthe toxic gas were removed from the vehicle within a few minutes afterthe accident, then many of these propellants would be usable to inflateairbags.

Much of the energy released when sodium azide burns in the inflator isremoved from the gas by the cooling and filtering screens. In somedesigns, the sodium oxide must be trapped by the filters, which requiresthat the gas be cooled to the point where sodium oxide condenses. In alldesigns, the gas is cooled so that the temperature of the gas in theairbag will not cause burns to the occupants. It is believed that in allcurrent designs, a substantial amount of the energy in a propellant islost through this cooling process which in turn necessitates that theinflator contains more propellant.

Airbag systems have primarily been installed within the instrument panelor steering wheel of automobiles. As a result, although numerousattempts have been made to create aspirated inflator systems, they haveonly been used on the passenger side and their efficiency has been low.In aspirated inflator systems, part of the gas to inflate the airbag isdrawn in from the passenger compartment. However, in a typical passengerside airbag system in use where aspiration is employed, substantiallyless than about 30% of the gas which inflates the airbag comes from thepassenger compartment and some researchers state that it is even belowabout 5%. In view of the large size of conventional sodium azideinflators and woven airbags, there is limited room for the airbag systemand it is difficult to design aspirating systems which will fit withinthe remaining available space. One reason is the resistance of the airflow through the instrument panel into the aspirator. Another reason forthe low efficiency of aspirated inflator systems is that the aspiratedsystems used typically have inefficient nozzle designs. Theoreticalstudies of aspiration systems, such as described herein, show that thepercentage of gas drawn in from the passenger compartment could beraised to as high as about 75% or even 90%.

As mentioned above, one airbag aspiration method is described in U.S.Pat. No. 4,909,549 to Poole et al. Poole et al. describes a method forinflating an airbag in which a substantially non-toxic primary gasmixture is diluted with outside air by passing the primary gas mixturethrough a venturi to aspirate the air. Poole et al. does not suggestthat the outside air should come from the passenger compartment andtherefore does not provide a solution to the problem of excessivepressure being generated in the passenger compartment upon deployment ofmultiple airbags, as discussed above.

If alternate, more efficient propellants are used and if the gasproduced thereby is exhausted at a much higher temperature, more of theenergy would be available to heat the gas which is flowing from thepassenger compartment to the airbag thus further increasing theefficiency of the system and reducing the amount of propellant required.Since cooling screens are not necessary and since the efficiency of thepropellant is high, the inflator can be made very small providing theextra space needed to design efficient aspirating nozzles.

Since many alternate propellants produce toxic gases, their use becomespractical (i) if the quantity used is substantially reduced, (ii) ifmeans are provided to prevent the gas from entering the occupantcompartment, and/or (iii) if means exist within the vehicle to exhaustthe toxic gas from the vehicle shortly after the airbag is deployed.

2.2.1 Plastic Inflator

There appears to be no related art suggesting the use of plastic for aninflator housing.

2.2.2 Vary Burn Rate

There appears to be no related art to an arbitrary control of the rateof burning of the inflator propellant through variation in thecross-sectional shape of the propellant and thus its burning rate,although there is discussion in several references that the burn rate isproportional to the surface area that is burning.

2.2.3 Liquid Propellant

There appears to be no related art suggesting the use of a liquidpropellant with as aspirated inflator design.

2.2.4 Propellant Considerations

There appears to be little related art suggesting that slightly toxicpropellants can be used with an aspirated inflator.

2.2.5 Cover Considerations

There appears to be no related art suggesting how an airbag cover can beefficiently removed from an elongated airbag module having an aspiratedinflator.

2.3 Controlling Amount of Gas in the Airbag

The amount of gas in an airbag can be controlled by controlling the ratethat the inflator produces gas, the amount of the produced gas thatactually enters the airbag and/or the outflow of the gas from theairbag.

2.3.1 Production of Gas

Primitive control of the production of the gas production first appearedin U.S. Pat. No. 4,380,346 where different thickness foils are placedover various exit orifices such that the flow is restricted from exitingthe inflator until the pressure reached the design value. U.S. Pat. No.5,772,238 is an early disclosure of the concept of varying the size ofan exit orifice as a function of the pressure within the inflator tocontrol the mass flow of gas out of the inflator. Subsequent patentsincluding U.S. Pat. Nos. 5,951,040, 5,984,352, 6,142,515, 6,227,565,6,290,256, 6,314,889, 6,315,322, 6,543,805, 6,655,712, 6,702,323 and USpublished Pat. Application 2004/0145166 have further developed this flowcontrol principle. Of particular interest are U.S. Pat. No. 6,314,889and US published Pat. Application 2004/0145166 which discuss thevariation in the flow based on the measurement of “at least one chosenproduct gas performance factor.”

2.3.2 Control Module

U.S. Pat. No. 6,532,408 is an early disclosure of a control moduledesigned to control the inflow and outflow of gas from an airbag whichimplies that any such method including variable control of inflator gasproduction is considered. Such a control module takes into account suchfactors as seat occupancy, classification of the seat occupant, positionor the seat occupant, severity of the crash etc. Some of these featureswere later discussed in U.S. Pat. No. 6,314,889 and US published Pat.Application 2004/0145166.

2.3.3 Control of Gas Outflow

See section 3.8.

2.4 Exhausting Inflator Gas

2.4.1 Removing Window

There appears to be no related art suggesting the intention breaking ofa window to allow a path for the excess pressure created when manyairbags are deployed and when there is toxic gas emitted.

2.4.2 Exhaust Airbag from Vehicle

There appears to be little related art suggesting the exhausting of theinflator gases outside of the passenger compartment.

2.4.3 Blow Out Panel

There appears to be no related art suggesting the exhausting of theinflator gases outside of the passenger compartment through the use of ablow out panel.

2.4.4 Exhaust Fan

There appears to be no related art suggesting the exhausting of theinflator gases outside of the passenger compartment through the use ofan exhaust fan.

3 Airbags

3.1 Plastic Film Airbags

Plastic films have not previously been used to make airbags with theexception of perforated films as disclosed in U.S. Pat. No. 4,963,412 toKokeguchi, which is discussed below.

U.S. Pat. No. 3,451,693 (Carey) describes the presence of a variableexhaust orifice in an airbag which maintains constant pressure in theairbag as the occupant is thrown into the airbag but does not discloseplastic film, merely plastic. The distinguishable properties of film arenumerically described in the instant specification and basically arethinner and less weight. The material of Carey is not plastic film whichis capable of arresting the propagation of a tear. In fact, it isunclear in Carey as to whether the orifice can be varied in arepeatable/reusable manner and no mention is made as to whether thestretching of the orifice area is permanent or temporary.

U.S. Pat. No. 5,811,506 (Slagel) describes a thermoplastic, elastomericpolyurethane for use in making vehicular airbags. The polyurethane isextrudable so that airbags of various shapes and sizes can be formedtherefrom.

U.S. Pat. No. 6,627,275 (Chen) describes the use of crystal gels toachieve tear resistance for airbags. This is a particular example of theteachings herein for the use of the thermoplastic elastomers to achievetear resistance through the use of a particular subclass of suchpolymers. No mention is made, however, to laminate these materials witha film with a higher elastic modulus as is taught herein. Althoughinteresting materials, they may not be practical for airbags due totheir high cost. In particular, the crystal gel described in Chen ispart of a class of thermoplastic elastomer (TPE) and in particular ofpolyester elastomers such as HYTREL™ which are discussed elsewhereherein and in the parent applications listed above. It is important tonote that the particular formulations listed in Chen are probably poorchoices for the blunting film portion of a laminated film used to makefilm airbags. This is due to their very high elasticity of 10⁴ to 10⁶dynes per cm² (see Chen at col. 21, line 4). This corresponds to theliquid crystal polymers which have an elastic modulus of above 10¹⁰dynes per cm². Thus, they will provide little resistance to thepropagation of a tear in the higher modulus component of the laminatedfilm and would be poor as the blunting layer.

It is important to note that liquid crystal polymers of a different sortthan disclosed in Chen having quite the opposite properties would beideal candidates for the high modulus component of a laminated film dueto their inelastic nature, that is their high modulus of elasticity.Although these materials are considerably more expensive than NYLON®,for example, they are about twice as strong and therefore only half asmuch would be required. This would render the inner layer, for example,of a lamination with perhaps urethane as the outer layers, half thethickness and thus one eighth of the bending stiffness of NYLON®. Thus,the laminated airbag made in this manner would be considerably easier tofold and when folded, it would occupy substantially less space.

Another advantage of the more rigid liquid crystal polymers is that theycan be laminated to polyurethane or other blunting materials without theneed for an adhesive. This results in a significant cost saving for thelaminated film and thus partially offsets the higher cost of thematerial compared with NYLON®, for example. Naturally, they can also belaminated to a more elastic liquid crystal polymer.

Note also that the “soft, safe, hugging, enveloping inflatable restraintcushions” described in Chen are not applicable in the form disclosedbecause, if used in a thin film version, it would blow up like a balloonpermitting the occupant to easily displace the gas and penetrate farinto the airbag. If used in a thick film version so that it does notstretch, then the advantages of the material are lost and the airbagwould be similar in weight to a fabric airbag. However, if it islaminated to a more rigid material or a net as disclosed herein and inthe previous patents of the current assignee, then again many of theadvantages of the material are lost since the main material providingthe strength to the airbag is the more rigid film or net layer.Nevertheless, providing there is not too much of a cost penalty the“elastic-crystalline gels” described in Chen might be advantageouslyused in the inventions described herein for some applications. Someother patents assigned to the same assignee as Chen that may be relevantto inventions herein are: U.S. Pat. Nos. 6,552,109, 6,420,475, 6,333,3746,324,703, 6,148,830, 6,117,176, 6,050,871, 5,962,572, 5,884,639,5,868,597, 5,760,117, 5,655,947, 5,633,286, 5,508,334, 5,336,708,5,334,646, 5,324,222, 5,262,468 and 4,369,284.

Although airbags are now installed in all new vehicles and each year anincreasing number of airbags are making their way into new vehicledesigns, they are still basically the same design as originally inventedabout 40 years ago. Generally, each driver and passenger side airbag isa single chamber or at most two chambers, they are made from fabric thathas sufficient mass as to cause injury to an occupant that is in thedeployment path and they are positioned so that a forward-facingoccupant will be protected in a substantially frontal impact. Incontrast, many occupants are out-of-position and many real world crashesinvolved highly angular impacts, spinouts, rollovers etc. where theoccupant is frequently injured by the deploying airbag and impacts otherobjects in the vehicle compartment in addition to the airbag.

In the out-of-position case, occupant sensors are now being consideredto prevent or control the deployment of the airbag to minimizedeployment induced injuries. These occupant sensors will significantlyreduce the number of deaths caused by airbags but in doing so, they candeprive the occupant of the protection afforded by a softer airbag ifthe deployment is suppressed. Side and side curtain airbags are beinginstalled to give additional protection to occupants in side impacts androllovers. However, there still will be many situations where occupantswill continue to be injured in crashes where airbags could have been asignificant aid. What is needed is an airbag system that totallysurrounds the occupant and holds him or her in the position that he orshe is prior to the crash. The airbag system needs to deploy veryrapidly, contact the occupant without causing injury and prevent his orher motion until the crash is over. This is a system that fills up thepassenger compartment in substantially the same way that packagingmaterial is used to prevent breakage of a crystal glass during shipment.

To accomplish this self-adjusting airbag system, the airbags must bemade of very light material so that when they impact the occupant, theydo not cause injury. They also must be inflated largely with the gasthat is in the passenger compartment or else serious ear injuries mayresult and the doors and windows may be blown out. Thus, an airbagsystem comprised of many mini-airbags all connected together andinflated with one or more aspirated inflators that limit the pressurewithin each mini-airbag is needed. This is one focus of this invention.As it is accomplished, the inflators will get smaller and simpler sincethere will be no need for dual stage inflators. Since out-of-positionoccupants will not be injured by the deploying airbags, there will be noneed for occupant sensors and children can safely ride in the front seatof a vehicle. The entire system will deploy regardless of the directionof the impact and the occupants will be frozen in their pre-crashpositions until the crash is over.

Anticipatory crash sensors based on pattern recognition technology aredisclosed in several of current assignee's patents and pending patentapplications (see, e.g., U.S. Pat. Nos. 6,343,810, 6,209,909, 6,623,033,6,746,078 and US20020166710). The technology now exists to allow theidentification and relative velocity determination to be made for anyairbag-required accident prior to the accident occurring (anticipatorysensing). This achievement now allows airbags to be reliably deployedprior to the accident. The implications of this are significant. Priorto this achievement, the airbag system had to wait until an accidentstarted before a determination could be made whether to deploy theairbags. The result is that the occupants, especially if unbelted, wouldfrequently achieve a significant velocity relative to the vehiclepassenger compartment before the airbags began to interact with theoccupant and reduce his or her relative velocity. This would frequentlysubject the occupant to high accelerations, in some cases in excess of40 Gs, and in many cases result in serious injury or death to theoccupant. On the other hand, a vehicle typically undergoes less than amaximum of 20 Gs during even the most severe crashes. Most occupants canwithstand 20 Gs with little or no injury. Thus, as taught herein, if theaccident severity could be forecast prior to impact and the vehiclefilled with plastic film airbags that freeze the occupants in theirpre-crash positions, many lives could be saved and many injuriesavoided.

A main argument against anticipatory sensors is that the mass of theimpacting object remains unknown until the accident commences. However,through using a camera, or other imaging technology based on, e.g.,infrared, radar or terahertz generators and receivers, to monitorpotentially impacting objects and pattern recognition technologies suchas neural networks, the object can be identified and in the case ofanother vehicle, the mass of the vehicle when it is in the unloadedcondition can be found from a stored table in the vehicle system. If thevehicle is a commercial truck, then whether it is loaded or not willhave little effect on the severity of an accident. Also if the relativevelocity of the impacting vehicles is above some threshold, then againthe mass of the impacting vehicle is not important to the deploymentdecision. Pickup trucks and vans are thus the main concern because asloaded, they can perhaps weigh 50 percent more than when unloaded.However, such vehicles are usually within 10% of theirunloaded-plus-one-passenger weight almost all of the time. Since thedecision to be made is whether or not to deploy the airbag, in allsevere cases and most marginal cases, the correct decision will be madeto deploy the airbag regardless if there is additional weight in thevehicle. If the assumption is made that such vehicles are loaded with nomore than 10% additional weight, then only in a few marginal crashes, ano-deployment decision will be made when a deployment decision iscorrect. However, as soon as the accident commences, the traditionalcrash sensors will detect the accident and deploy the airbags, but forthose marginal cases the occupants will have obtained little relativeforward velocity anyway and probably not be hurt and certainly notkilled by the deploying plastic film airbags which stop deploying assoon as the occupant is contacted. Thus, the combination of anticipatorysensor technology and plastic film airbags as disclosed herein resultsin the next generation self adapting safety system that maximizesoccupant protection. Both technologies preferably can be used together.

Another feature of plastic film airbags discussed below is the abilityof film to be easily joined together to form structures that would bedifficult or impossible to achieve with fabric such as the addition of asheet of film to span the chambers of a side curtain airbag. It is wellknown that side curtain airbags are formed with chambers in order tolimit the thickness of the curtain. This results in a curtain withreduced stiffness to resist the impact of the head of an occupant, forexample, and to also form areas where the protection is less than otherareas due to the presence of seams. Using film, these seam sections canbe easily spanned without running the risk of introducing additionalleakage paths in the airbag. This spanning of the chambers can produceadditional chambers that can also be pressurized or the additionalchambers can be left open to the atmosphere.

An analysis of a driver airbag made from two flat sheets of inelasticfilm shows that maximum stresses occur in the center of the airbag wherethe curvature is at a minimum. Thus, the material strength and not theseal or seam strength limits the pressure that causes the airbag tofail. On the other hand, analysis of some conventional side curtainairbags has shown that maximum stress can occur in the seams and thusthe maximum pressure that the airbag can hold without bursting islimited by the material strength in the seams. This fact is at leastpartially the cause of excessive gas leakage at the seams of some fabricairbags necessitating the lamination of a polymer film onto the outsideof the airbag. This problem is even more evident when the bag is made bycontinuous weaving where the chambers are formed by weaving two sheetsof material together. A solution to this problem as discussed below isto first optimize the design of the seam area to reduce stresses andthen to form the airbag by joining the sheets of material by heatsealing, for example, where an elastic material forms the seam thatjoins the sheets together. Such a joint permits the material to stretchand smooth the stresses, eliminating the stress concentrations and againplacing the maximum stresses in the material at locations away from theseam. This has the overall effect of permitting the airbag to beconstructed from thinner material permitting a more rapid deployment andcausing less injury to an out-of-position occupant. This technique alsofacilitates the use of plastic film as an airbag material. Such a filmcan comprise a relatively inelastic, biaxially oriented layer formaximum tensile strength and a relatively elastic, polyurethane film, orequivalent, where the polyurethane film is substantially thicker thanthe NYLON®. This combination not only improves the blunting propertydiscussed above but also substantially reduces the stresses in the seams(see Appendix 3).

U.S. Pat. No. 6,355,123 to Baker et al. uses reinforcement material tomake the seams stronger so as to compensate for the increased stressesdiscussed above rather than using elastic material to smooth out thestresses as disclosed herein. Similarly, in U.S. Pat. No. 6,712,920,Masuda et al. add reinforcing strips to the inside of a seam which areattached by adhesive to the airbag beyond the sewn seam.

3.2 Driver Side Airbag

A conventional driver side airbag (also referred to herein as a driverairbag) is made from pieces of either NYLON® or polyester fabric thatare joined together, e.g., by sewing. The airbag is usually coated onthe inside with neoprene or silicone for the purposes of (i) capturinghot particles emitted by the inflator in order to prevent holes frombeing burned in the fabric, and (ii) sealing the airbag to minimize theleakage of an inflating gas through the fabric. Although such coatingsare films, they differ significantly from the films disclosed herein inthat they do not significantly modify the properties of the fabricairbags to which they are applied since they are thin and substantiallymore elastic than fabric. These airbags are conventionally made by firstcutting two approximately circular sections of a material having acoating on only one side and which will form a front panel and a backpanel, and sewing them together with the coated side facing out. Theback panel is provided with a hole for attachment to an inflator. Fabricstraps, called tethers, are then sewn to the front panel. Afterwards,the airbag is turned inside out by pulling the fabric assembly throughthe inflator attachment hole placing the coated side on the inside.Assembly is completed by sewing the tethers to the back panel adjacentthe inflator attachment hole.

If a conventional driver airbag is inflated without the use of tethers,the airbag will usually take an approximately spherical shape. Such aninflated airbag would protrude significantly into the passengercompartment from the steering wheel and, in most cases, impact andinjure the driver. To prevent this possible injury, the tethers areattached to the front and rear panels of the airbag to restrict thedisplacement of the front panel relative to the back panel. The resultof the addition of such tethers is an airbag that has the shape of aflat ellipsoid with a ratio of the thickness of the airbag to itsdiameter of approximately 0.6. In the conventional airbag, the tethersare needed since the threads that make up the airbag fabric are capableof moving slightly relative to each other. The airbag is elastic forstresses that are not aligned with the warp or roof of the fabric. As aresult, the fabric would distort to form an approximate sphere in theabsence of such tethers.

Moreover, the above-mentioned method of manufacturing an airbag involvesa great deal of sewing and thus is highly labor intensive and, as aresult, a large percentage of all driver airbags are presentlymanufactured in low labor cost countries such as Mexico.

Many people are injured and some killed by interaction with thedeploying airbag (see, e.g., “Warning: Too Much Safety May BeHazardous”, New York Times, Sunday, Dec. 10, 1995, Section F, Page 8).One of the key advantages of the film airbag described herein and in thecurrent assignee's above-referenced patents and patent applications isthat, because of its much lower mass than conventional NYLON® orpolyester fabric airbags, the injury caused by interaction with thedeploying airbag is substantially reduced. In accordance with theteachings of those patents and patent applications mentioned above, thedriver airbag system can be designed to permit significant interactionwith the driver. In other words, the film airbag can be safely designedto intrude substantially further into the passenger compartment withoutfear of injuring the driver. Nevertheless, in some cases, as describedin U.S. Pat. No. 5,653,464, it may be desirable to combine theproperties of a film airbag, which automatically attains theconventional driver airbag shape, with a fabric airbag. In such cases,interaction with the driver needs to be minimized.

Airbag systems today are designed so that ideally the airbag is fullyinflated before the occupant moves into the space that is occupied bythe airbag. However, most occupants are not positioned at the ideallocation assumed by the airbag system designer, and also may not havethe dimensions, e.g., size and weight, in the range considered foroptimum airbag deployment by the airbag system designer. Many occupantssit very close to the airbags, or at least closer than expected by theairbag system designer, and as mentioned above, are injured by theairbag deployment. On the other hand, others sit far from the airbag, orat least farther away from the airbag than expected, and therefore musttravel some distance, achieving a significant relative velocity, beforereceiving the benefit of the airbag (see, e.g., “How People Sit in Cars:Implications For Driver and Passenger Safety in Frontal Collisions—TheCase for Smart Restraints.”, Cullen, E., et al 40^(th) AnnualProceedings, Association For the Advancement of Automotive Medicine, pp.77-91).

With conventionally mounted airbags such as those mounted in thesteering wheel or instrument panel, severe out-of-position occupantsituations, for example where the occupant is resting against the airbagwhen deployment begins, can be handled using an occupant positionsensor, such as disclosed in the current assignee's U.S. Pat. No.5,653,462 (corresponding to WO 94/22693) which prevents an airbag fromdeploying if an occupant is more likely to be seriously injured by theairbag deployment than from the accident itself. In many less severeaccidents, the occupant will still interact with the deploying airbagand sustain injuries ranging from the mild to the severe. In addition,as mentioned above, some occupants sit very far from the steering wheelor instrument panel and, with conventional airbags, a significantdistance remains between the occupant and the inflated airbag. Suchoccupants can attain a significant kinetic energy relative to the airbagbefore impacting it, which must be absorbed by the airbag. This effectserves to both increase the design strength requirements of the airbagand increase the injury induced in the occupant by the airbag. For thesereasons, it is desirable to have an airbag system that adjusts to thelocation of the occupant and which is designed so that the impact of theairbag causes little or no injury to the occupant.

Conventional airbags contain orifices or vent holes for exhausting orventing the gas generated by the inflator. Thus, typically for frontalimpact airbags within one second after the bag is inflated (and hasprovided its impact absorbing function), the gas has been completelyexhausted from the bag through the vent holes. This imposes severallimitations on the restraint system that encompasses the airbag system.Take for example the case where an occupant is wearing a seatbelt andhas a marginal accident, such as hitting and severing a small tree,which is sufficient to deploy the airbag, but where it is not reallyneeded since the driver is being restrained by his seatbelt. If thedriver has lost control of the car and is traveling at 30 MPH, forexample, and has a secondary impact one second or about 50 feet later,this time with a large tree, the airbag will have become deflated andthus is not available to protect the occupant in this secondary, lifethreatening impact.

In other situations, the occupant might be involved in an accident thatexceeds the design capability of the restraint system. These systems aretypically designed to protect an average-size male occupant in a 30-MPHbarrier impact. At higher velocities, the maximum chest decelerationexperienced by the occupant can exceed 60 G's and become lifethreatening. This is particularly a problem in smaller vehicles, whereairbag systems typically only marginally meet the 60-G maximumrequirement, or with larger or frailer occupants.

There are many cases, particularly in marginal crashes, where existingcrash sensors will cause the airbag to deploy late in the crash. Thiscan also result in an “out-of-position occupant” for deployment of theairbag that can cause injuries and possibly death to the occupant. Othercases of out-of-position occupants include standing children or theforward motion of occupants during panic braking prior to impactespecially when they are not wearing seatbelts. The deploying airbag inthese situations can cause injury or death to the out-of-positionoccupant. It is estimated that more than one hundred people have nowbeen killed and countless more seriously injured by the deployment ofthe airbag due to being out-of-position.

It is recognized in the art that the airbag must be available to protectan occupant for at least the first 100-200 milliseconds of the crash andlonger for rollover events. Since the airbag usually contains largevents, the inflator must continue to supply gas to the airbag to replacethe gas flowing out of these vents. As a result, inflators are usuallydesigned to produce about twice as much gas than is needed to fill theairbag for frontal impacts. This, of course, increases the cost of theairbag system as well as its size, weight, pressure in the passengercompartment and total amount of contaminants resulting from the gasesthat are exhausted into the automobile environment.

This problem is compounded when the airbag becomes larger, which is nowpossible using the film materials of this invention, so as to impactwith the occupant wherever he/she is sitting, without causingsignificant injury, as in a preferred implementation of this invention.This then requires an even larger inflator which, in many cases, cannotbe accommodated in conjunction with the steering wheel, if conventionalinflator technology, rather than an aspirated inflator, is utilized.

Furthermore, there is a great deal of concern today for the safety of achild in a rear facing child seat when it is used in the front passengerseat of a passenger airbag equipped vehicle. Current passenger sideairbags have sufficient force to cause significant injury to a childsitting in such a seat and parents are warned not to use child seats inthe front seat of a vehicle having a passenger side airbag.Additionally, several automobile companies are now experimenting withrear seat airbags in which case, the child seat problem would becompounded.

Airbags made of plastic film are described in the patents and patentapplications referenced above. Many films are quite inelastic undertypical stresses associated with an airbag deployment. If an airbag ismade from a pair of joined flat circular sections of such films andinflated, instead of forming a spherical shape, it automatically formsthe flat ellipsoidal shape required for driver airbags as described inU.S. Pat. No. 5,653,464. This unexpected result vastly simplifies themanufacturing process for driver airbags since tethers are not required,i.e., the film airbag is made from two pieces of film connected only attheir peripheral edges. Furthermore, since the airbag can be made byheat-sealing two flat circular sections together at their peripheraledges without the need for tethers, the entire airbag can be madewithout sewing, thereby reducing labor and production costs. In fact,the removal of the requirement for tethers permits the airbag to be madeby a blow molding or similar process which greatly reduces the cost ofmanufacturing driver airbags. Thus, the use of film for making an airbaghas many advantages that are not obvious.

Films having this inelastic quality, that is films with a high modulusof elasticity and low elongation at failure, tend to propagate tearseasily and thus when used alone are not suitable for airbags. Thisproblem can be solved through the addition of reinforcement inconjunction with the inelastic films such as a net material as describedin the above-referenced patents and patent applications. Other moreelastic films such as those made from the thermoplastic elastomers, onthe other hand, have a low modulus of elasticity and large elongation atfailure, sometimes 100%, 200% or even 400%, and naturally resist thepropagation of tears. Such films, on the other hand, do not form theflat ellipsoidal shape desired for steering wheel-mounted driver sideairbags. As discussed in greater detail below, the combination of thetwo types of film through attachment using lamination, successivecasting or coating, or through the use of adhesives, which can beapplied in a pattern, can produce a material having both theself-shaping and the resistance to tear propagation properties.

In addition to the above-referenced patents and patent applications,film material for use in making airbags is described in U.S. Pat. No.4,963,412 to Kokeguchi. The film airbag material described in Kokeguchiis considerably different in concept from that disclosed in the currentassignee's above-referenced patents and patent applications or theinstant invention. The prime feature of Kokeguchi is that the edge tearresistance, or notch tear resistance, of the airbag film material can beincreased through the use of holes in the plastic films, i.e., the filmis perforated. Adding holes, however, reduces the tensile strength ofthe material by a factor of two or more due to the stress concentrationeffects of the hole. It also reduces the amount of available material toresist the stress. As such, it is noteworthy that the Kokeguchi steeringwheel mounted airbag is only slightly thinner than the conventionaldriver side fabric airbag (320 micrometers (0.013 inches) vs. theconventional 400 micrometers) and is likely to be as heavy as or perhapsheavier than the conventional airbag. Also, Kokeguchi does not discloseany particular shapes of film airbags or even the airbag itself for thatmatter. Since his airbag has no significant weight advantage overconventional airbags, there is no teaching in Kokeguchi of perhaps themost important advantage of thin film airbags of the present invention,that is, in reducing injuries to occupants who interact with a deployingairbag.

In some implementations of the film airbag of the present invention, theconcept of “blunting” is used to achieve the property of arresting thepropagation of a tear (see, e.g., Weiss, Peter “Blunt Answer: Crackingthe puzzle of elastic solids' toughness”, Science News, Week of Apr. 26,2003, Vol. 163, No. 17).

As discussed in detail below, the airbags constructed in accordance withthe present teachings attain particular shapes based on the use of theinelastic properties of particular film materials and reduce tearpropagation through a variety of novel methods including the use ofelastic films and blunting that is achieved by combinations of filmswith different elastic moduli. It is also noteworthy that Kokeguchidescribes using vacuum methods to form the airbag into the desired shapeand thus fails to realize that the properties of inelastic film resultsin the airbag automatically forming the correct shape upon deployment.Also noteworthy is that Kokeguchi states that polymeric films do nothave sufficient edge tear resistance and thus fails to realize thatfilms can be so formulated to have this property, particularly thosemade incorporating elastomers. These limitations of Kokeguchi results ina very thick airbag that although comprised of film layers, no longerqualifies as a true film airbag as defined herein.

A “film airbag” for the purposes herein is one wherein the filmthickness is generally less than about 250 micrometers (0.01 inches),and preferably even below about 100 micrometers, for use as a driverprotection airbag. As the size of the airbag increases, the thicknessmust also increase in order to maintain an acceptable stress within thefilm. A film airbag so defined may also contain one or more sectionsthat are thicker than about 250 micrometers and which are used primarilyto reinforce the thinner film portion(s) of the airbag. A film airbag asdefined herein may also include a layer or layers of inelastic materialand a layer or layers of elastic material (for example thermoplasticelastomers).

The neoprene or silicone coating on conventional driver airbags, asmentioned above, serves to trap hot particles that are emitted from someinflators, such as a conventional sodium azide inflator. A film airbagmay be vulnerable to such particles, depending on its design, and as aresult, cleaner inflators that emit fewer particles are preferred overmost sodium azide inflators. It is noteworthy, however, that even if ahole is burned through the film by a hot particle, the use of anelastomer in the film material prevents this hole from propagating andcausing the airbag to fail, that is by blunting the crack or tearpropagation. Also, new inflators using pyrotechnic, hybrid, aspirated orstored gas technologies are now available which do not produce hotparticles and produce gases which are substantially cooler than gasesproduced by sodium azide inflators. Also, not all sodium azide inflatorsproduce significant quantities of hot particles.

One interesting point that also is not widely appreciated by thoseskilled in the art previously, is that the gas temperature from theinflator is only an issue in the choice of airbag materials during theinitial stages of the inflation. The total thermal energy of the gas inan airbag is, to a first order approximation, independent of the gastemperature which can be shown by application of the ideal gas laws.When the gas initially impinges on the airbag material during the earlystages of the inflation process, the temperature is important and, if itis high, care must be taken to protect the material from the gas. Also,the temperature of the gas in the airbag is important if the vent holesare located where the out-flowing gas can impinge on an occupant. Theaverage temperature of the airbag itself, however, will not be affectedsignificantly by the temperature of the gas in the airbag.

In certain conventional airbag deployments, the propellant which is usedto inflate the airbag also is used to force open a hole in the vehicletrim, called the deployment door, permitting the airbag to deploy. Sincethe mass of a film airbag is substantially less than the mass of aconventional fabric airbag, much less energy is required to deploy theairbag in time. However, substantial pressure is still required to openthe deployment door. Also, if the pressure now used to open thedeployment door is used with film airbags, the airbag velocity once thedoor has been opened may be substantially higher than conventionalairbags. This rapid deployment can put excessive stresses on the filmairbag and increases the chance that the occupant will be injuredthereby. For most implementations of the film airbag, an alternate lessenergetic method of opening the deployment door may be required.

One such system is described in Barnes et al. (U.S. Pat. No. 5,390,950)entitled “Method and arrangement for forming an airbag deploymentopening in an auto interior trim piece”. This patent describes a method“ . . . of forming an airbag deployment opening in an interior trimpiece having a vinyl skin overlying a rigid substrate so as to beinvisible prior to operation of the airbag system comprising an energygenerating linear cutting element arranged in a door pattern beneath theskin acting to degrade or cut the skin when activated.”

A goal of Barnes et al. is to create an invisible seam when thedeployment door is located in a visible interior trim panel. Thispermits greater freedom for the vehicle interior designer to create theparticular aesthetic effect that he or she desires. The invisible seamof Barnes et al. is thus created for aesthetic purposes with no thoughttoward any advantages it might have to reduce occupant injury oradvantages for use with a film airbag, or to reduce injuries at all forthat matter. One unexpected result of applying the teachings of thispatent is that the pressure required to open the deployment door,resulting from the force of the inflating airbag, is substantiallyreduced. When used in conjunction with a film airbag, this result isimportant since the inflator can be designed to provide only sufficientenergy to deploy and inflate the very light film airbag therebysignificantly reducing the size of the inflator. The additional energyrequired to open a conventional deployment door, above that required toopen a deployment door constructed in accordance with the teachings ofBarnes et al., is not required to be generated by the inflator.Furthermore, since a film airbag can be more vulnerable to being injuredby ragged edges on the deployment door than a conventional fabricairbag, the device of Barnes et al. can be used to pyrotechnically cutopen the deployment door permitting it to be easily displaced from thepath of the deploying airbag, minimizing the force of the airbag againstthe door and thus minimizing the risk of damage to the film airbag fromthe deployment door. Since Barnes et al. did not contemplate a filmairbag, advantages of its use with the pyrotechnically openingdeployment door could not have been foreseen. Although Barnes et al.describes one deployment door opening method which is suitable for usewith an airbag made from plastic film as disclosed herein, i.e., onewhich requires substantially less force or pressure to open thanconventional deployment doors, other methods can be used in accordancewith the invention without deviating from the scope and spirit thereof.

The discussion of the self-shaping airbag thus far has been limited tofilm airbags. An alternate approach is to make an airbag from acombination of fabric and film. The fabric provides the tear resistanceand conventional airbag appearance. The film forces the airbag toacquire the flat ellipsoidal shape desired for driver airbags withoutthe use of tethers and permits the airbag to be assembled without sewingusing heat and/or adhesive sealing techniques. Such a hybrid airbag ismade from fabric and film that have been laminated together prior to thecutting operation. A combination of a film and net, as described in theabove referenced patents and patent applications, is equally applicablefor airbags described here and both will be referred to herein as hybridairbags and belong to the class of composite airbags. Combinations of afilm and fabric in this invention differ from previous neoprene orsilicone coated fabric airbags in that in the prior art cases, thecoating does not materially effect either the elastic modulus,stiffness, strength or tear resistance of the airbag whereas ininventions disclosed herein, the film contributes significantly to oneor more of these properties.

A finite element analysis of conventional driver side airbags (made offabric) shows that the distribution of stresses is highly unequal.Substantial improvements in conventional airbag designs can be made byredesigning the fabric panels so that the stresses are more equalized(see, e.g., Appendix 1 of U.S. patent application Ser. No. 10/974,919which describe inventive designs of airbags with fabric panels andrelatively more equalized stresses and Appendices 1-6 of U.S. patentapplication Ser. No. 10/817,379 filed Apr. 2, 2004, both of which areincorporated by reference herein). Today, conventional airbags aredesigned based on the strength required to support the maximum stressregardless of where that stress occurs. The entire airbag must then bemade of the same thickness material as that selected to withstandmaximum stress condition. This is wasteful of material and attempts havebeen made to redesign the airbag to optimize its design in order to moreclosely equalize the stress distribution and permit a reduction infabric strength and thus thickness and weight. However, thisoptimization process when used with conventional fabric airbags can leadto more complicated assembly and sewing operations and more expensivewoven materials and thus higher overall manufacturing costs. An exampleof such an airbag is that marketed by Precision Fabrics of Greensboro,N.C. Thus, there is a tradeoff between manufacturing cost and airbagoptimization.

As discussed in the above-referenced patents and patent applications aswell as below and in Appendix 1 of the '919 application and Appendices1-6 of the '379 application, with a film airbag manufactured using blowmolding or casting techniques, for example, greater freedom is permittedto optimize the airbag vis-à-vis equalization of the stress. First,other than tooling cost, the manufacturing cost of an optimized airbagis no greater than for a non-optimized airbag and in fact frequentlyless since less material is required. Furthermore, the thickness of thefilm can be varied from one part of the airbag to another to permit theairbag to be thicker where the stresses are greater and thinner wherethe stresses are less. A further advantage of blow molding or casting isthat the film can be made of a single constituent material. When theairbag is fabricated from sheet material, the outside layer of thematerial needs to be heat sealable, such as is the case withpolyurethane, polyethylene or other polyolefin, or else a specialadhesive layer is required where the sealing occurs.

As discussed in greater detail below in connection with the descriptionof the invention, when the film for the airbag is manufactured bycasting or coating methods, techniques familiar to those skilled in theart of plastics manufacturing are also available to produce a film wherethe thickness varies from one part to another in a predeterminedpattern. This permits a film to be made that incorporates thickersections in the form of a lattice, for example, which are joinedtogether with thin film. Thus, the film can be designed so thatreinforcing ribs, for example, are placed at the optimum locationsdetermined by mathematical stress analysis.

One example of an inflatable film product which partially illustratesthe self-shaping technology of this invention is the common balloon madefrom metalized MYLAR® plastic film found in many stores. Frequentlythese balloons are filled with helium. They are made by heat-sealing twoflat pieces of film together as described in U.S. Pat. No. 5,188,558(Barton), U.S. Pat. No. 5,248,275 (McGrath), U.S. Pat. No. 5,279,873(Oike) and U.S. Pat. No. 5,295,892 (Felton). Surprisingly, the shape ofthese balloons, which is circular in one plane and elliptical in theother two planes, is very nearly the shape that is desired for a driverside airbag. This shape is created when the pressure within the balloonis sufficiently low such that the stresses induced into the film aremuch smaller than the stresses needed to significantly stretch the film.The film used is relatively rigid and has difficulty adjusting to form aspherical shape. In contrast, the same airbag made from woven materialmore easily assumes an approximate spherical shape requiring the use oftethers to create the shape which comes naturally with the MYLAR®balloons.

One problem with film balloons is that when a hole is formed in theballoon, it fails catastrophically. One solution to this problem is touse a combination of a film and net as described in the currentassignee's above-referenced patents and patent applications. Suchmaterials have been perfected for use as sail material for lightweighthigh performance sails for sailboats. One example is marketed under thetrade name Bainbridge Sailcloth SL Series™, and in particular SL 500-P™,0.0015 inches. This material is a laminate of a film and a net. Suchmaterials are frequently designed to permit heat-sealing therebyeliminating threads and the stress concentrations associated therewith.Heat-sealing also simplifies the manufacturing process for making sails.Another preferred solution is to make the airbags from a film materialwhich naturally resists tears, that is, one which is chemicallyformulated to arrest a tear which begins from a hole, for example.Examples of films which exhibit this property are those from thethermoplastic elastomer (TPE) families such as polyurethane, Ecdelelastomer from Eastmen, polyester elastomers such as HYTREL™ and somemetallocene-catalyzed polyolefins. For the purposes herein, athermoplastic elastomer will include all plastic films which have arelatively low modulus of elasticity and high elongation at failure,including but not limited to those listed above. As discussed below, inmany implementations, the elastomers can be laminated with NYLON® (NYLON6,6 for example) or other more rigid film to form a composite filmhaving the blunting property.

Applications for the self-shaping airbag described herein include allairbags within the vehicle which would otherwise require tethers orcomplicated manufacturing from several separate panels. Most of theseapplications are more difficult to solve or unsolvable usingconventional sewing technology. The invention described herein solvessome of the above problems by using the inelastic properties of film,and others by using the elastic properties of thermoplastic elastomersplus innovative designs based on analysis including mathematicalmodeling plus experimentation (see Appendix 1 of the '919 applicationand Appendices 1-6 of the '379 application). In this manner, theproblems discussed above, as well as many others, are alleviated orsolved by the airbags described below. Films for airbags which exhibitboth the self-shaping property and also formulated to resist thepropagation of a tear are made by combining a layer of high modulusmaterial with a layer of a thermoplastic elastomer. Then, if a tearbegins in the combined film, it will be prevented from propagating bythe elastomer, yet the airbag will take the proper shape due to theself-shaping effect of the high modulus film. Such materials frequentlyexhibit blunting.

Japanese Patent No. 89-090412/12 describes fabricated cloths that arelaminated in layers at different angles to each other's warp axis to beintegrated with each other. Strength and isotropy are improved. Thecloth is stated as being useful for automotive airbags for protectingthe passenger's body. It is possible that such an airbag may have someof the self-shaping properties of a driver side film airbag disclosedherein but such is not disclosed in this patent.

U.S. Pat. Nos. 6,607,796 and 6,180,044 (Hirai) describe a plastic filmdriver side airbag referred to as a Resin airbag and a method of makingit. One layer of the film airbag is actually molded in place resultingin a variation in material thickness at the seams. This variation inthickness has also been disclosed in the current assignee's patents aslisted above. The resulting bag has a variation in the shape caused bythe variable width of the seam. In the current assignee's patents, asimilar effect is achieved by varying the geometry of the seam asillustrated herein in FIG. 75D.

Consider now a driver side airbag that does not rotate with the steeringwheel. Self-contained driver side airbag systems, such as U.S. Pat. No.4,167,276 to Bell and U.S. Pat. No. 4,580,810 to Thuen, are designed tomount on and rotate with the steering wheel of vehicles. Such designshave the advantage of being modular so that they can be installed onmany different vehicles with a modification of the steering wheel.However, because the airbag module rotates with the steering wheel, theshape of a driver side airbag must be axis-symmetrical with respect tothe axis of steering wheel, as is the case with conventional driverairbags. This configuration allows the airbag to deploy and provide auniform protection at any steering position. Usually a driver sideairbag is made of two circular pieces of coated NYLON® cloth sewntogether with tethers and becomes an approximation of an ellipsoid wheninflated.

An airbag absorbs the energy of an occupant when the occupant movesforward and impacts with the airbag and the airbag deforms to wraparound the occupant. The efficiency of an airbag cushion depends notonly on the stiffness and damping of the bag (which is a function of thepressure inside the bag and the exit orifices or exit valves), but alsoon the relative orientation and penetration of the occupant and the bag.If a large portion of the occupant torso is in contact with the bag inthe early stage of a crash, a considerable amount of occupant energy canbe dissipated. On the other hand, if only a small portion of the body,such as the head, is in contact with the bag, it can result insignificant penetration into the bag and delay the absorption of kineticenergy. Airbags of axis-symmetrical shapes may not be optimal foroccupant protection because the interaction between an airbag and anoccupant is a function of the distance and the relative angle betweenthe steering wheel and the occupant's upper torso. Another concern isthat the steering wheel angle can change significantly from driver todriver

Another problem of an ellipsoidal driver side bag is the tendency of thedriver to slide off edges of the bag particularly in angle crashes. Thisis mainly due to the geometry of the bag and the fact that the centralportion of the bag is frequently stiffer than the periphery. A solutionis to have a larger airbag, like a passenger side airbag, to embrace thedriver as much as possible to prevent the tendency to slide off theairbag. Such improvements cannot be achieved by a driver side airbagfixed to the steering wheel because the space and the geometry are bothlimited.

Some vehicles, such as buses and trucks, have a very steep steeringcolumn angle. When an accident occurs and the driver moves forward, thelower part of the steering wheel close to the driver makes contact withthe driver first and a great deal of abdomen or chest penetrationoccurs. If a conventional airbag module attached to the steering wheelis deployed, the protection of driver is limited until the upper torsoof the driver bends fully forward and lands on the air cushion. Thisproblem could be solved by modifying the angle of the steering wheel orcolumn, but it requires a change of the structure of the steeringmechanism or the installation of an additional joint in the steeringcolumn.

Inside a self-contained airbag module, the sensor is arranged so thatits axis is aligned to the axis of the steering wheel. The axis of thesensor is defined as the sensitive axis of the accelerometer or sensingmass. However, a ball-in-tube sensor or an accelerometer-based satellitecrush zone mounted sensor used to detect frontal impacts has thesensitive axis parallel to the longitudinal axis of the vehicle. Withsuch an arrangement, the sensor is most sensitive in the desireddetecting direction. In the self-contained module mounted on thesteering wheel, on the other hand, the sensitivity of the sensor to thefrontal velocity change is reduced because the sensor is inclined at anangle from the crushing direction. Even though the calibration of asensor can be chosen selected to compensate the steering column angle,this makes the sensor more sensitive to vertical accelerations which maybe undesirable.

In many cases, the driver side airbag module located on the steeringwheel is large and frequently blocks the driver's view of the instrumentpanel behind the steering wheel. When this is the case, the addition ofan airbag system to a vehicle can require modification of the steeringcolumn or the instrument panel to compensate for this reducedvisibility.

The steering column of some vehicles may collapse or shift in ahigh-speed crash or under a tremendous crush of the front end of avehicle. If the driver side airbag is designed to operate under normalconditions, the unexpected movement of the steering column could changethe location of a deployed airbag and thus alter the relative positionsof the occupant and the airbag cushion. This can result in a partialloss of airbag protection for the driver.

US20040026909 to Rensingoff describes an auxiliary airbag coming fromthe dashboard to support the steering wheel and provide additionalprotection to the driver through this supplemental airbag. Such anairbag is not disclosed to aid in supporting a much lighter steeringwheel steering column as might be used in a drive-by-wire system.

3.3 Passenger Side Airbag

There is no known related art specifically covering passenger airbagsmade from plastic film.

3.4 Inflatable Knee Bolster

This aspect of the invention relates to a knee bolster safety apparatusfor protecting the legs and lower torso of the occupant of a motorvehicle to reduce the extent and severity of injuries sustained during acrash. This invention more specifically relates to using an inflatablebolster to restrain the occupant's legs and lower torso during asurvivable crash.

During a frontal impact, the occupant moves forward due to the inertiaand kinematics of the crash while the front components of the vehiclestructure (bumper, hood, engine cavity) begin to collapse. Knee and leginjuries can occur when the body of an occupant slides or submarinesforward and/or downward and the occupant's knees hit the instrumentpanel or structure beneath the panel. Further injuries can occur whenthe occupant's lower torso and legs move forward such that the knees aretrapped in or beneath the instrument panel just before the foot wellbegins to collapse. As the foot well collapses, it can push theoccupant's feet backward, causing the knees to elevate and becomefurther trapped. As the foot well continues to crush, the loads on thetrapped legs increase and can cause foot, ankle, and tibia injuries.These injuries are common even with fixed knee bolsters designed to meetpresent knee injury criteria requirements.

Abdominal and lower torso injuries can be inflicted by the lap and lowerpart of the torso belts as they ride upward on the soft tissue of theoccupant's torso when he or she slides forward and downward due to theforces of the frontal crash. Knee bolsters are designed to attempt toeliminate or minimize these injuries.

Airbag apparatus are generally designed under the assumption that theoccupant is riding in the vehicle in a forward-facing, seated positionwith both feet on the vehicle floor. When an occupant is not in thisposition, the occupant or occupant's body part is said to be“out-of-position”. As most occupants are sometimes out-of-position,airbag apparatus which effectively restrain the occupant regardless ofthe occupant's position are advantageous.

During a front end collision with a standard airbag, if the occupant isrestrained by a seat belt, the occupant's upper torso bends at the waistand hits the primary airbag. However, depending on the design of thevehicle seat and force of the collision, there is a tendency for anoccupant to slide forward along the seat and slip below the primaryairbag, sometimes even entering into leg compartment of the vehicle.Alternatively, the legs and knees of the occupant may slide or shift toone side of the seat or the other. The tendency is pronounced when theoccupant is not properly restrained by a seat belt. This tendency may bereferred to as “submarining”. Submarining often causes the occupant'supper torso to bend at the waist but not in a direction perpendicular tothe primary airbag. When the occupant submarines, the primary airbag isless effective in protecting the occupant.

Submarining is more prevalent in vehicles which have large leg roomcompartments. Vehicles which have restricted leg room, such as sportscars, have a lower submarining tendency. In vehicles like sports cars,the distance between the legs and knees of the occupant and theinstrument panel is shorter than the distance in vehicles such as sportutility vehicles or trucks. In an accident in a sports car, the knees ofthe occupant often strike the instrument panel. The instrument panelthen prevents submarining. Generally, the material of the sports carinstrument panel deforms to some degree to help protect the legs andknees of the occupant. The area of the instrument panel which isimpacted is called the knee bolster.

In order to prevent submarining in vehicles with large leg roomcompartments, a knee airbag system is sometimes used. A knee airbagsystem is generally positioned in the lower portion of the instrumentpanel. Knee airbag systems allow vehicle manufacturers to designvehicles with more leg room and still have safety comparable to that ofvehicles with less leg room.

The knee airbag system includes an inflator, a housing, an airbag, and atrim cover panel. The housing is a conventional enclosure for securingthe knee airbag components to the vehicle. The housing stores the kneeairbag system components while the airbag is deflated and not in use.

The airbag provides the main structure for protecting the occupant. Thebag is generally made of flexible fabric material. The material isgenerally a weave of NYLON® and/or polyester. Generally, multiple piecesof fabric are sewn together to form an airbag. Alternatively, thematerial may be woven to create a one piece airbag. Preferably, astaught herein, the airbag is formed into cells and made from plasticfilm.

The trim cover panel is a panel which covers the airbag and inflatorwithin the housing and presents an aesthetic trim surface to the vehicleoccupant. The trim cover panel is connected to the housing such that thepressure of the inflating airbag pushes the trim cover panel out of theway.

The inflator, once triggered, uses compressed gas, solid fuel, or acombination to produce rapidly expanding gas to inflate the airbag. Aswith conventional airbag systems, a knee airbag can be a large textilebag which the gas inflates like a balloon. The conventional prior artinflated knee airbag occupies some of the volume of the vehicle legcompartment. The knee airbag system may also include a fixed panel,called a load distribution panel or knee bolster panel. This panel canbe made of foam and hard plastic surrounding a metal substrate. Thispanel can provide support to prevent submarining.

Generally, two designs are used in knee airbag systems. The first designconcentrates on moving a piece of rigid material, similar to thematerial of the instrument panel in a sports car, close to theoccupant's knees and legs thereby creating leg and knee support. This isknown as a load distribution plate. The second design does not use asupport plate. This design relies on the knee airbag to provide thenecessary knee and leg support. Traditional designs of the knee airbagwithout the load distribution plate have been less successful inpreventing submarining. This is due to the fact that the airbag onlypartially fills the volume surrounding the knees and legs of theoccupant and thus the airbag can easily deform and provides lesssupport. On the other hand, it is possible for the knees of the occupantto slip off of the load distribution plate thereby defeating itspurpose. Also, if the load distribution plate is at a significantdistance from the occupant's knees, the occupant can attain asignificant velocity before striking the plate resulting in knee andfemur injuries.

These problems are generally solved by the cellular knee bolster designdescribed in detail herein.

It is known in the art to make an inflatable fabric single chamber kneebolster airbag without a load distribution panel. U.S. Pat. Nos.3,642,303 and 5,240,283 are two of many such patents. It is also knownto use an airbag to move a load distribution panel closer to theoccupant (see, e.g., U.S. Pat. Nos. 6,345,838, 6,471,242 and EuropeanPatent EP00684164B1).

U.S. Pat. No. 4,360,223 (Kirchoff) describes a low-mount, airbag modulefor the passenger side of an automobile that uses two bags that arefolded within a housing that is open at one end. One of the bags is forrestraining the knees of the passenger to prevent forward sliding in theevent of a crash, the other bag is for restraining the torso. The kneebag is inside the torso bag and they are both attached directly to theinflator, the knee bag being arranged to be inflated first. The torsobag then is inflated to prevent forward rotation of the passenger fromthe hips.

Further, in accordance with Kirchoff, a pressure responsive orifice isprovided in a second opening in the wall of the knee bag. This orificecontrols the flow of gas through the opening in the wall of the knee bagthereby to insure a predetermined gas pressure within the knee bag,while permitting subsequent inflation of the torso bag by gases passinginto the torso bag through the orifice. Thus, a knee bolster airbag isdescribed but it is positioned inside of the main torso airbag andinflated by the same inflator.

U.S. Pat. No. 5,458,366 describes a compartmentalized airbag thatfunctions to move a knee bolster or load distribution plate to the kneesof the occupant. The occupant's knees do not contact directly thecompartmentalized airbag as is in a preferred embodiment of theinvention as described herein below. The '366 patent correctly pointsout that a knee bolster airbag, referred to in the '366 patent as areactive type knee bolster, functions on the principle of a singlecompartment airbag and has the disadvantage that on impact of the kneeswith the airbag, the airbag loses rigidity in the impact area. This isdue to the gas flowing from the impact area to other parts of theairbag.

U.S. Pat. No. 6,092,836 also describes an airbag that moves a loaddistribution plate toward the occupant's knees. This patent points outthat using known knee bolsters, the knees of an improperly seatedoccupant can slide off the knee bolster potentially increasing thetendency of the occupant to submarine under the instrument panel. It isimportant that the knee bolster capture the knees to prevent thisproblem, as is an object of the present invention.

Another problem pointed out by the '836 patent is the tendency, due tothe point loading, for the knees in many airbag knee bolsters topenetrate too far into the bolster and therefore lose some of the energyabsorbing effects. Thus, most knee bolsters use a load distributionplate for the contact point with the occupant's knees. This will also beaddressed in the description of the invention below.

U.S. Pat. No. 6,170,871 describes an unworkable elastic film airbag as aknee bolster. The fact that an elastic film is used results in the airflowing from the point of contact to another unloaded section which thenexpands as a balloon. There is also a danger that if punctured, the '871knee bolster will pop as a balloon since it will not exhibit blunting asdescribed below. One properly designed film knee bolster, as disclosedbelow, makes use of a laminated film material including a layer of ahigh modulus of elasticity film with one or more layers of film having alow elastic modulus. The combination does not expand as a balloon as inthe case of the '871 patent and thus its shape is accurately controlled.Also, if it should get punctured, the hole or tear does not propagate.

U.S. Pat. No. 6,336,653 (Yaniv et al.) describes an inflatable tubularbolster that is meant to reduce leg and knee injuries and prevent theoccupant from submarining under the instrument panel. This designsuffers from the tendency of the occupant's knees to slide off of thebolster if the accident is from an angle or if the occupant is notproperly seated.

US20020149187 (Holtz et al.) describes a soft knee bolster which isbasically composed of cells of fabric airbag material positioned infront of a load distribution plate. The knee bolster of the presentinvention also provides for a soft knee bolster but usually does notrequire a special load distribution or reaction plate. This patentapplication correctly points out that, it would advance the art toprovide a soft-surface inflatable knee bolster airbag system whichprevents submarining while providing a soft surface for contacting avehicle occupant's legs and knees. It would be another advancement inthe art to provide a soft-surface inflatable knee bolster airbag systemwhich functions even though the occupant's legs and knees are“out-of-position”. A further advancement in the art would be to providea soft-surface inflatable knee bolster airbag system which is compact,simple, and has fewer parts. The present invention provides theseadvancements in a novel and useful way. All of these advancements areavailable in the cellular bolster as first described in the currentassignee's U.S. Pat. No. 5,505,485.

U.S. Pat. No. 6,685,217 describes a flat mattress like airbag, similarto those disclosed in assignee's prior patents, for use as a kneerestraint.

Thus, there are no known knee bolster airbags that are made from plasticfilm or that are made from interconnecting compartments that predatethose disclosed by the assignee.

3.5 Ceiling Deployed Airbags

U.S. Pat. No. 5,322,326 (Ohm) describes a small, limited protectionairbag manufactured in Korea. Although not disclosed in the patent, itappears to use a plastic film airbag material made from polyurethane. Itis a small airbag and does not meet U.S. standards for occupantprotection (FMVSS-208). The film has a uniform thickness and if scaledto the size necessary for meeting U.S. standards, it would likely becomeof comparable thickness and weight as the current fabric airbags.

Of particular interest, FIG. 6 shows an airbag having a shape thatconforms to the human body by forming a two-fold pocket bag. Junctionpoints are provided such that after inflation, the head of a passengeris protected by an inflated part around the upper junction point whilethe upper part of the passenger is covered with the other inflated partaround the middle junction points and a U-shaped junction line. Incontrast to some pertinent inventions disclosed below, the junctionpoints and lines do not enable the formation of an airbag having aplurality of substantially straight or elongate compartments, or even amultiplicity of cells, which can be deployed along the side of a vehiclein order to protect the occupant(s) from injury. Rather, the junctionpoints and lines result in the formation of a limited-use airbag whichwill conform only to the human body, i.e., having a section for engagingthe head and a section for engaging the upper body. Other applicationsof junction points and lines are not contemplated by Ohm.

3.5.1 Side Curtain Airbags

U.S. Pat. No. 5,439,247 describes a fabric hose and quilt-type airbagthat is meant to protect front seat occupants in side impacts. Theconstruction has a rectangular peripheral tube with an inner sectionformed by stitching the fabric together to form cells or tubes. Asidefrom the fact that this is made from fabric, there is no discussion asto how this airbag is supported during a crash and it appears likelythat the bag will be pushed out the window by the head of the occupant.Although it is mentioned that the airbag can be deployed from either thedoor or the ceiling, it does not extend into the rear section of thevehicle passenger compartment. There appears to be no prior art sidecurtain airbags made from fabric that predate the disclosure in thecurrent assignee's patents listed above. There also is no prior art formaking a side curtain airbag from plastic film.

U.S. Pat. No. 6,457,745 (Heigl) describes how to achieve the effects oftethers without actually having them. In this case, loose threads areused as if they were a seam to permit the weaving of a fabric airbag andat the same time to achieve control over the shape of the resultingairbag. In particular, for side curtain airbags, it can be desirable tohave a roughly uniform thickness across the entire front and rear seatspan except where the seat back would interfere. However, to achievethis ideal would require many tethers since left to its own, the airbagswould tend to form spherical-like chambers. As stated in the currentassignee's patents on film airbags, this is by nature less of a problemwith film since the tendency of inelastic film is to form ellipsoidsrather than spheres which is the tendency of fabric. However, this isnot the only advantage of film in this arena as will be seen below.Since sheets of plastic film can be easily manufactured in any thicknessand since they can be easily joined using either heat or adhesivesealing, the opportunities for controlling film geometry greatly exceedthat of fabric. Thus, by practicing the teachings of this invention,very substantial benefits accrue, as will be shown below.

3.5.2 Frontal Curtain Airbags

With the exception of U.S. Pat. No. 5,322,326 discussed above, thereappears to be no other prior art on ceiling-mounted airbags for frontalcrash protection and none whatsoever that extend so as to offerprotection for multiple occupants.

3.5.3 Other Compartmentalized Airbags

U.S. Pat. No. 3,511,519 (Martin) describes a large fabric airbag whichis shown impacting the occupant. It does not discuss the problem ofinjury to the occupants due to the impact of the airbag which wouldcertainly be the case with this design.

U.S. Pat. No. 4,262,931 (Strasser) describes two airbags joined togetherto cover right and center seating positions. These airbags are notmounted on the vehicle ceiling.

U.S. Pat. No. 3,638,755 (Sack) describes a two-bag airbag combination,however, one bag is contained within the other.

U.S. Pat. No. 3,752,501 (Daniel) describes an inflatable cushion devicefor protective interposition between a vehicle operator and the rim andhub of a vehicle steering wheel assembly. The cushion is compartmentedto provide, when inflated, peripheral ring compartmentation injuxtaposition to the steering wheel rim and center compartmentation inoverlying juxtaposition to the steering wheel hub. The peripheral ringcompartmentation, when pressurized, provides greater resistance tocollapse than the center compartmentation, whereby the peripheral ringcompartmentation is adapted to guide the vehicle operator upon contactof the latter with the cushion toward the center compartmentationthereby maintaining the vehicle operator in substantially centeredcushioned relationship to the steering wheel assembly under vehicleimpact conditions. This airbag contains two compartments; an outer,donut-shaped ring or torus, and an inner compartment of somewhat largervolume. This is an example of a bag within a bag where an outer bag isconnected to an inner bag by flapper valves.

U.S. Pat. No. 4,227,717 (Bouvier) describes a method for protecting amotorcycle operator with a plurality of tubular plastic or fabricairbags. These tubes deploy upward from a housing mounted on themotorcycle.

3.6 Rear-of-Seat Mounted Airbags

There is minimal, if any, prior art for rear-of-seat mounted airbags ofthe type described herein.

3.7 Exterior Airbags

There is minimal, if any, prior art for exterior mounted airbags madefrom plastic film.

3.8 Variable Vent

U.S. Pat. No. 3,573,885 (Brawn) describes a blowout patch assembly butnot variable exhaust orifices.

U.S. Pat. No. 3,820,814 (Allgaier) describes variable exhaust ventslocated within the fabric airbag material.

U.S. Pat. No. 3,888,504 (Bonn) describes an inflatable occupantrestraint airbag which is comprised at least in part of a woven stretchfabric which is permeable to fluid used to inflate the bag, the baghaving a variable porosity which increases and decreases in relation tothe fluid pressure within the bag.

U.S. Pat. No. 4,394,033 (Goetz) describes a temperature compensationsystem. The inflatable occupant-restraint system in a vehicle includes agenerator for producing fluid under pressure placed such that a portionof the generator is outside the cushion and has a resilient ventingstructure for dumping increasing fractions of gas volume outside thecushion at increasing operating temperatures.

U.S. Pat. No. 4,805,930 (Takada) describes another temperaturecompensation system. Further, it describes stitched thread seams betweenfabric elements of the envelope of a vehicle safety airbag which inducelocalized distension and opening up of the envelope fabrics along theseams, thereby causing the film coatings of the envelope fabric torupture along the seam and allow gas to escape and maintain asubstantially constant overall maximum pressure, regardless ofvariations in ambient temperature.

U.S. Pat. No. 3,675,942 (Huber) describes a unidirectional valve whichpermits air to enter the bag, but prevents its escape in the event thepressure within the bag exceeds that of the atmosphere within thevehicle, such as by the impact of a person with the bag.

U.S. Pat. No. 4,964,652 (Karlow) describes a system for ventingexcessively high pressure gas incident to deployment of an airbagincluding a diaphragm that is rupturable upon the occurrence of athreshold pressure internally of the airbag to instantaneously releasethe pressure. This is a pressure relief system through the center of themodule.

3.8.1 Discharge Valves for Airbags

Prior art valves for possible use with airbags includes those describedin U.S. Pat. No. 4,719,943 (Perach), and U.S. Pat. No. 5,855,228(Perach).

Also, U.S. Pat. No. 5,653,464 (Breed et al.) discloses a variable venthole for an airbag (FIGS. 7 and 7A). The variable vent is formed in aseam of the airbag and includes a hinged elastic member biased so thatit tends to maintain the vent in a closed position. As pressure rises inthe airbag, the vent is forced open. The vent contains an opening formedbetween a film layer of the airbag and a reinforcement member. The filmlayer is also sealed to the reinforcing member

Flow of gas out of an airbag may be controlled during inflation anddeflation of the airbag based on the morphology of the occupant for whomdeployment of the airbag will be effective as disclosed in U.S. Pat. No.5,822,707 (Breed et al.). This patent, as well as others assigned to thecurrent assignee, further describes that gas outflow may also becontrolled based on other properties of the occupant to be protected bythe deploying airbag including but not limited to the occupant'sposition, identification and/or type.

3.9 Airbags with a Barrier Coating

Barrier coatings which prevent, or reduce, contact of a selectedsubstrate with a gas, vapor, chemical and/or aroma have been widelydescribed. A recent improvement in barrier coatings is described in U.S.Pat. No. 6,087,016 and U.S. Pat. No. 6,232,389.

To date, barrier coatings have not been commercially applied in airbagsmade of fabric and in particular side curtain airbags made of fabricwhich is often permeable. It would thus be desirable to improve theimpermeability of the fabric of the airbags.

In contrast to frontal impact driver and passenger airbags which onlyare required to retain the inflation gas or other fluid for typically afraction of a second, the side curtain airbag must retain the inflationfluid for several seconds in order to offer protection for rolloverevents, for example. Also, the side curtain or ceiling-mounted airbagmust deploy rapidly and pack into a small space.

It is disadvantageous that current polymer coatings used on such airbagsare relatively thick thereby increasing the mass of the airbag making itdifficult to pack into a ceiling space and delay the deployment of theairbag in an accident, thereby increasing the chance that an occupantwill not receive the full benefit of the airbag. As a result of thesedisadvantages, such coatings are not optimal for use on side curtainairbags.

Much of the leakage in side curtain airbags occurs through the seamswhere the front and rear panels forming the side curtain airbag arejoined. This is due to the methods of joining such panels which includesewing and interweaving. Thus, although the barrier coatings of thisinvention will reduce the leakage through the panel surfaces, and reducethe cost and mass of the airbag, alternative treatments for the seamarea are also desirable as described and disclosed herein.

4 Systems

4.1 Self-Contained Airbag Systems

Self-contained airbag systems contain all of the parts of the airbagsystem within a single package, in the case of mechanicalimplementations, and in the case of electrical or electronic systems,all parts except the primary source of electrical power and, in somecases, the diagnostic system. This includes the sensor, inflator andairbag. Potentially, these systems have significant cost and reliabilityadvantages over conventional systems where the sensor(s), diagnostic andbackup power supply are mounted separate from the airbag module. Inmechanical implementations in particular, all of the wiring, thediagnostic system and backup power supply are eliminated. In spite ofthese advantages, self-contained airbag systems have only achievedlimited acceptance for frontal impacts and have so far not beenconsidered for side impacts.

The “all-mechanical” self-contained systems were the first to appear onthe market for frontal impacts but have not been widely adoptedpartially due to their sensitivity to accelerations in the vertical andlateral directions. These cross-axis accelerations have been shown toseriously degrade the performance of the most common all mechanicaldesign that is disclosed in Thuen, U.S. Pat. No. 4,580,810. Both frontaland side impact crashes frequently have severe cross-axis accelerations.

Additionally, all-mechanical self-contained airbag systems, such asdisclosed in the Thuen patent, require that the sensor be placed insideof the inflator which increases the strength requirements of theinflator walls and thus increases the size and weight of the system. Onesolution to this problem appears in Breed, U.S. Pat. No. 4,711,466, buthas not been implemented. This patent describes a method of initiatingan inflator through the use of a percussion primer in combination with astab primer and the placement of the sensor outside of the inflator. Onedisadvantage of this system is that a hole must still be placed in theinflator wall to accommodate the percussion primer that has its ownhousing. This hole weakens the wall of the inflator and also provides apotential path for gas to escape.

Another disadvantage in the Thuen system that makes it unusable for sideimpacts is that the arming system is sealed from the environment by anO-ring. This sealing method may perform satisfactorily when the systemis mounted in the protected passenger compartment but it would not besatisfactory for side impact cases where the system would be mounted inthe vehicle door where it can be subjected to water, salt, dirt, andother harsh environments.

Self-contained electrical systems also appear not to have been used.When airbags are used for both the driver and the passenger,self-contained airbag systems require a separate sensor and diagnosticfor each module. In contrast to mechanical systems, the electronicsensor and diagnostic systems used by most vehicle manufacturers areexpensive. This duplication and associated cost required for electricalsystems eliminates some of the advantages of the self-contained system.

Sensors located in the passenger compartment of a vehicle can catch mostairbag-required crashes for frontal impacts, particularly if theoccupants are wearing seatbelts. Also, if the teachings of thisinvention are practiced where an algorithm based on pattern recognitionis used, then almost all frontal crash can be sensed in time in thepassenger compartment. Mechanical sensors, however, are not capable ofimplementing such algorithms and thus researchers now believe that thereare a significant number of crashes that cannot be sensed in time in thepassenger compartment by mechanical sensors and that this will requirethe addition of another sensor mounted in the crush zone (see, forexample, reference 5). If true, this will eventually eliminate the useof mechanical self-contained airbag systems for frontal impacts.

Some of these problems do not apply to side impacts mainly because sideimpact sensors must trigger in a very few milliseconds when there is nosignificant signal at any point in the vehicle except where the car iscrushing or at locations rigidly attached to this crush zone. Eachairbag system can be mounted in the crush zone and generally will haveits own sensor. Self-contained airbag systems have previously not beenused for occupant protection for side impacts, which is largely due tothe misconception that side impact sensing requires the use of elongatedswitches as is discussed in detail in U.S. Pat. No. 5,231,253. Theseelongated side impact crush-sensing switches are not readily adaptableto the more compact self-contained designs. The realization that amoving mass sensor was the proper method for sensing side impacts hasnow led to the development of the side impact self-contained airbagsystem of this invention. The theory of sensing side impacts is includedin the '253 patent referenced above.

In electro-mechanical and electronic self-contained modules, the backuppower supply and diagnostic system can be mounted apart from the airbagsystem. If a wire is severed during a crash but before the airbagdeploys, the system may lose its power and fail to deploy. This is morelikely to happen in a side impact where the wires are inside the door.For this reason, mechanical self-contained systems have a significantreliability advantage over conventional electrical or electronic systemsfor side impacts.

Finally, the space available for mounting airbag systems in the doors ofvehicles is frequently severely limited making it desirable that theairbag module be as small as possible. Conventional gas generators usesodium azide as the gas generating propellant. This requires that thegas be cooled and extensively filtered to remove the sodium oxide, atoxic product of combustion. This is because the gas is exhausted intothe passenger compartment where it can burn an occupant and be inhaled.If the gas is not permitted to enter the passenger compartment, thetemperature of the gas can be higher and the products of combustion cancontain toxic chemicals, such as carbon dioxide.

These and other problems associated with self-contained airbag systemsand side impact sensors are solved by the invention disclosed herein.

4.2 Occupant Sensing

Automobiles equipped with airbags are well known in the prior art. Insuch airbag systems, the car crash is sensed and the airbags rapidlyinflated thereby insuring the safety of an occupation in a car crash.Many lives have now been saved by such airbag systems. However,depending on the seated state of an occupant, there are cases where hisor her life cannot be saved even by present airbag systems. For example,when a passenger is seated on the front passenger seat in a positionother than a forward facing, normal state, e.g., when the passenger isout of position and near the deployment door of the airbag, there willbe cases when the occupant will be seriously injured or even killed bythe deployment of the airbag.

Also, sometimes a child seat is placed on the passenger seat in a rearfacing position and there are cases where a child sitting in such a seathas been seriously injured or killed by the deployment of the airbag.

Furthermore, in the case of a vacant seat, there is no need to deploy anairbag, and in such a case, deploying the airbag is undesirable due to ahigh replacement cost and possible release of toxic gases into thepassenger compartment as well as potentially causing injury to occupantsdue to high pressure within the passenger compartment. Nevertheless,most airbag systems will deploy the airbag in a vehicle crash even ifthe seat is unoccupied.

Thus, whereas thousands of lives have been saved by airbags, a largenumber of people have also been injured, some seriously, by deployingairbags, and over 100 people have now been killed. Thus, significantimprovements need to be made to airbag systems. As discussed in U.S.Pat. No. 5,653,462, for a variety of reasons vehicle occupants may betoo close to the airbag before it deploys and can be seriously injuredor killed as a result of the deployment thereof. Also, a child in a rearfacing child seat that is placed on the right front passenger seat is indanger of being seriously injured if the passenger airbag deploys. Forthese reasons and, as first publicly disclosed in reference 14, occupantposition sensing and rear facing child seat detection systems arerequired in order to minimize the damages caused by deploying front andside airbags. It also may be required in order to minimize the damagecaused by the deployment of other types of occupant protection and/orrestraint devices that might be installed in the vehicle.

For these reasons, there has been proposed an occupant sensor systemalso known as a seated-state detecting unit such as disclosed in thefollowing U.S. patents assigned to the current assignee of the presentapplication: Breed et al. (U.S. Pat. No. 5,563,462); Breed et al. (U.S.Pat. No. 5,829,782); Breed et al. (U.S. Pat. No. 5,822,707): Breed etal. (U.S. Pat. No. 5,694,320); Breed et al. (U.S. Pat. No. 5,748,473);Varga et al. (U.S. Pat. No. 5,943,295); Breed et al. (U.S. Pat. No.6,078,854); Breed et al. (U.S. Pat. No. 6,081,757); and Breed et al.(U.S. Pat. No. 6,242,701). Typically, in some of these designs, three orfour sensors or sets of sensors are installed at three or four points ina vehicle for transmitting ultrasonic or electromagnetic waves towardthe passenger or driver's seat and receiving the reflected waves. Usingappropriate hardware and software, the approximate configuration of theoccupancy of either the passenger or driver seat can be determinedthereby identifying and categorizing the occupancy of the relevant seat.

4.3 Controlling Airbag Inflation

There are many ways to control inflation of the airbag and several arenow under development by inflator companies, the current assignee andothers. One way is to divide the airbag into different charges and toinitiate these charges independently as a function of time to controlairbag inflation. An alternative is to always generate the maximumamount of gas but to control the amount going into the airbag, dumpingthe rest into the atmosphere. A third way is to put all of the gas intothe airbag but control the outflow of the gas from the airbag through avariable vent valve. For the purposes herein, all controllable apparatusfor varying the gas flow into and/or out of the airbag over time will beconsidered as a gas control module whether the decision is made at thetime of initial airbag deployment, at one or more discrete times lateror continuously during the crash event.

4.4 Diagnostics

Every automobile driver fears that his or her vehicle will breakdown atsome unfortunate time, e.g., when he or she is traveling at night,during rush hour, or on a long trip away from home. To help alleviatethat fear, certain luxury automobile manufacturers provide roadsideservice in the event of a breakdown. Nevertheless, unless the vehicle isequipped with OnStar® or an equivalent service, the vehicle driver muststill be able to get to a telephone to call for service. It is also afact that many people purchase a new automobile out of fear of abreakdown with their current vehicle. This invention is also concernedwith preventing breakdowns and with minimizing maintenance costs bypredicting component failure that would lead to such a breakdown beforeit occurs.

When a vehicle component begins to fail, the repair cost is frequentlyminimal if the impending failure of the component is caught early, butincreases as the repair is delayed. Sometimes if a component in need ofrepair is not caught in a timely manner, the component, and particularlythe impending failure thereof, can cause other components of the vehicleto deteriorate. One example is where the water pump fails graduallyuntil the vehicle overheats and blows a head gasket. It is desirable,therefore, to determine that a vehicle component is about to fail asearly as possible so as to minimize the probability of a breakdown andthe resulting repair costs.

There are various gages on an automobile which alert the driver tovarious vehicle problems. For example, if the oil pressure drops belowsome predetermined level, the driver is warned to stop his vehicleimmediately. Similarly, if the coolant temperature exceeds somepredetermined value, the driver is also warned to take immediatecorrective action. In these cases, the warning often comes too late asmost vehicle gages alert the driver after he or she can convenientlysolve the problem. Thus, what is needed is a component failure warningsystem that alerts the driver to the impending failure of a componentsufficiently in advance of the time when the problem gets to acatastrophic point.

Some astute drivers can sense changes in the performance of theirvehicle and correctly diagnose that a problem with a component is aboutto occur. Other drivers can sense that their vehicle is performingdifferently but they don't know why or when a component will fail orhowserious that failure will be, or possibly even what specific componentis the cause of the difference in performance. An invention disclosedherein will, in most cases, solve this problem by predicting componentfailures in time to permit maintenance and thus prevent vehiclebreakdowns.

Presently, automobile sensors in use are based on specific predeterminedor set levels, such as the coolant temperature or oil pressure, wherebyan increase above the set level or a decrease below the set level willactivate the sensor, rather than being based on changes in this levelover time. The rate at which coolant heats up, for example, can be animportant clue that some component in the cooling system is about tofail. There are no systems currently on automobiles to monitor thenumerous vehicle components over time and to compare componentperformance with normal performance. Nowhere in the vehicle is thevibration signal of a normally operating front wheel stored, forexample, or for that matter, any normal signal from any other vehiclecomponent. Additionally, there is no system currently existing on avehicle to look for erratic behavior of a vehicle component and to warnthe driver or the dealer that a component is misbehaving and istherefore likely to fail in the very near future.

Sometimes, when a component fails, a catastrophic accident results. Inthe Firestone tire case, for example, over 100 people were killed when atire of a Ford Explorer blew out which caused the Ford Explorer torollover. Similarly, other component failures can lead to loss ofcontrol of the vehicle and a subsequent accident. It is thus veryimportant to accurately forecast that such an event will take place butfurthermore, for those cases where the event takes place suddenlywithout warning, it is also important to diagnose the state of theentire vehicle, which in some cases can lead to automatic correctiveaction to prevent unstable vehicle motion or rollovers resulting in anaccident. Finally, an accurate diagnostic system for the entire vehiclecan determine much more accurately the severity of an automobile crashonce it has begun by knowing where the accident is taking place on thevehicle (e.g., the part of or location on the vehicle which is beingimpacted by an object) and what is colliding with the vehicle based on aknowledge of the force deflection characteristics of the vehicle at thatlocation. Therefore, in addition to a component diagnostic, theteachings of this invention also provide a diagnostic system for theentire vehicle prior to and during accidents. In particular, thisinvention is concerned with the simultaneous monitoring of multiplesensors on the vehicle so that the best possible determination of thestate of the vehicle can be determined. Current crash sensors operateindependently or at most one sensor may influence the threshold at whichanother sensor triggers a deployable restraint.

In the teachings of this invention, two or more sensors, frequentlyaccelerometers and/or gyroscopes, can be monitored simultaneously andthe combination of the outputs of these multiple sensors are combinedcontinuously in making the crash severity analysis. Also, according tothe teachings of this invention, all such devices can communicate on asingle safety bus that connects the various safety related electronics,sensors and actuators such as airbag modules, seatbelt retractors, andvehicle control systems.

4.5 Smart Airbags

Since there is often insufficient information in the acceleration data,as measured in the passenger compartment, to sense all crashes and sincesome of the failure modes of published single point sensor algorithmscan be easily demonstrated using the techniques of crash and velocityscaling described in the referenced technical papers, and moreover sincethe process by which engineers develop algorithms is generally based ontrial and error, pattern recognition techniques such as neural networkshould be able to be used to create an algorithm based on training thesystem on a large number of crash and non-crash events which, althoughnot perfect, will be superior to all others. This in fact has proved tobe true and is the subject of U.S. Pat. No. 5,684,701. That invention isbased on the ability of neural networks to forecast, based on the firstpart of the crash pulse, that the crash will be of a severity whichrequires that an airbag be deployed.

As will be discussed in detail below, an improvement on that invention,which is a subject of an invention herein, carries this process furtherby using a neural network pattern recognition system to forecast thevelocity change of the crash over time so that the inflation and/ordeflation of the airbag, and optionally the tensioning of the seatbelt,can be optimized. This invention further contemplates the addition ofthe pattern recognition occupant position and velocity determinationsystems disclosed in U.S. Pat. Nos. 5,829,782, 6,343,810 and U.S.RE37260. Finally, the addition of the weight of the occupant iscontemplated to provide a measure of the occupant's inertia or momentumas an input to the system. The combination of these systems in variousforms can be called “smart airbags” or “smart restraints” which will beused as equivalents herein. In a preferred implementation, the crashseverity is not explicitly forecasted but rather, the value of a controlparameter used to control flows of inflator gas into and/or out of theairbag is forecasted.

Smart airbags can take several forms which can be roughly categorizedinto four evolutionary stages, which will hereinafter be referred to asPhase 1 (2, 3 or 4) Smart Airbags, as follows:

1) Occupant sensors such as the disclosed in the U.S. patents and patentapplications referenced above use various technologies to turn off theairbag where there is a rear-facing child seat present or if either thedriver or passenger is out-of-position, i.e., in a position in whichhe/she is more likely to be injured by the airbag than from theaccident.

2) Occupant sensors will be used along with variable inflation and/ordeflation rate airbags to adjust the inflation/deflation rate to matchthe occupant first as to his/her position and then to his/hermorphology. The occupant sensors disclosed in the cross-referencedpatents and patent applications will also handle this with the possibleaddition of an occupant weighing system. One particular weight measuringsystem which makes use of strain gages mounted onto the seat supportingstructure is disclosed in U.S. Pat. No. 5,748,473, another that makesuse of a fluid filled bladder is disclosed in U.S. Pat. No. 6,442,504and still another uses a mat in the seat to measure the pressuredistribution of the occupant as disclosed in U.S. Pat. No. 6,412,357. Atthe end of this phase, little more can be done with occupant measurementor characterization systems.

3) The next improvement, and a subject of an invention disclosed herein,is to use a pattern recognition system such as neural networks as thebasis of a crash sensor system not only to determine if the airbagshould be deployed but also to predict the crash severity from thepattern of the initial portion of the crash pulse. Additionally, thecrash pulse will continue to be monitored even after the decision hasbeen made to deploy the airbag to see if the initial assumption of thecrash type based on the pattern up to the deployment decision wascorrect. If the pattern changes indicating a different crash type, theflow rate to the airbag can be altered on the fly, i.e., substantiallyinstantaneously. This crash sensor system can consist of a singleelectronic accelerometer-based passenger compartment sensor, a multiplesensor system that also includes either electronic or mechanical crushzone mounted sensors and in the most sophisticated cases, the passengercompartment sensor is replaced by an inertial measurement unit (IMU).Such an IMU can consist of up to three accelerometers and up to threegyroscopes, usually based on MEMS technologies. It can also be coupledto the vehicle navigation system whereby the accuracy of the IMU can beenhanced through a technique such as a Kalman filter and a GPS or DGPSsystem or other absolute positioning system. Of particular interest isan IMU disclosed in U.S. Pat. No. 4,711,125 with modifications.

4) Finally, anticipatory sensing, using radar, laser radar, acoustics,or cameras, and also using pattern recognition techniques such as neuralnetworks will be used to identify the crash before it takes place andselect the deployment characteristics of the airbag to match theanticipated crash with the occupant size and position. Such ananticipatory sensor is described in U.S. Pat. No. 6,343,810.

Any of these phases can be combined with various methods of controllingthe pretensioning, retraction and/or energy dissipation characteristicsof a seatbelt. Although a focus of an invention disclosed herein iscontrol of gas flows into and out of an airbag, it is to be recognizedthat control of the seatbelt, or any other restraint, can also benefitfrom the inventions herein and that the condition of the seatbelt can bevaluable input information into the pattern recognition system.

The smart airbag problem is complex and difficult to solve by ordinarymathematical methods. Looking first at the influence of the crash pulse,the variation of crash pulses in the real world is vast and quitedifferent from the typical crashes run by the automobile industry asreported in the technical papers referenced herein. It is one problem topredict that a crash has a severity level requiring the deployment of anairbag. It is quite a different problem to predict exactly what thevelocity versus time function will be and then to adjust the airbaginflation/deflation control system to make sure that just the properamount of gas is in the airbag at all times even without considering theinfluence of the occupant. To also simultaneously consider the influenceof occupant size, weight, position and/or velocity, renders this problemfor all practical purposes unsolvable by conventional methods.

On the other hand, if a pattern recognition system such as a neuralnetwork is used and trained on a large variety of crash accelerationsegments, as described in U.S. Pat. No. 5,684,701, and a setting for theinflation/deflation control system is specified for each segment, thenthe problem can be solved. Furthermore, inputs from the occupantposition and occupant weight sensors can also be included. The resultwill be a training set for the neural network involving many millions,and perhaps tens of millions, of data sets or vectors as everycombination of occupancy characteristics and acceleration segment isconsidered. Fortunately, the occupancy data can be acquiredindependently and is currently being done for solving theout-of-position problem of Phase 1 smart airbags. The crash data isavailable in abundance and more can be created using crash and velocityscaling techniques described in the papers referenced herein. Thetraining using combinations of the two data sets, which must also takeinto account occupant motion which is not adequately represented in theoccupancy data, can then be done by computer.

5 Definitions

An “IMU” is usually a self-contained device that usually has threeorthogonal accelerometers and three gyroscopes. In some cases, a smallernumber can be used. In U.S. Pat. No. 4,711,125, a single mass is used toachieve measurements of all six degrees of freedom.

“Pattern recognition” as used herein will generally mean any systemwhich processes a signal that is generated by an object (e.g.,representative of a pattern of returned or received impulses, waves orother physical property specific to and/or characteristic of and/orrepresentative of that object) or is modified by interacting with anobject, in order to determine to which one of a set of classes that theobject belongs. Such a system might determine only that the object is oris not a member of one specified class, or it might attempt to assignthe object to one of a larger set of specified classes, or find that itis not a member of any of the classes in the set. The object can also bea vehicle with an accelerometer that generates a signal based on thedeceleration of the vehicle. Such a system might determine only that theobject is or is not a member of one specified class (e.g.,airbag-required crashes), or it might attempt to assign the object toone of a larger set of specified classes, or find that it is not amember of any of the classes in the set. One such class might consist ofvehicles undergoing a crash of a certain severity into a pole. Thesignals processed are generally a series of electrical signals comingfrom transducers that are sensitive to acoustic (ultrasonic) orelectromagnetic radiation (e.g., visible light, infrared radiation,capacitance or electric and/or magnetic fields), although other sourcesof information are frequently included. Pattern recognition systemsgenerally involve the creation of a set of rules that permit the patternto be recognized. These rules can be created by fuzzy logic systems,statistical correlations, or through sensor fusion methodologies as wellas by trained pattern recognition systems such as neural networks,combination neural networks, cellular neural networks or support vectormachines or a neural computer.

A trainable or a trained pattern recognition system as used hereingenerally means a pattern recognition system that is taught to recognizevarious patterns constituted within the signals by subjecting the systemto a variety of examples. The most successful such system is the neuralnetwork used either singly or as a combination of neural networks. Thus,to generate the pattern recognition algorithm, test data is firstobtained which constitutes a plurality of sets of returned waves, orwave patterns, or other information radiated or obtained from an object(or from the space in which the object will be situated in the passengercompartment, i.e., the space above the seat) and an indication of theidentity of that object. A number of different objects, optionally indifferent positions, are tested to obtain the unique patterns from eachobject. As such, the algorithm is generated, and stored in a computerprocessor, and which can later be applied to provide the identity of anobject based on the wave pattern, for example, received during use by areceiver connected to the processor and other information. For thepurposes here, the identity of an object sometimes applies to not onlythe object itself but also to its location and/or orientation in thepassenger compartment. For example, a rear-facing child seat is adifferent object than a forward-facing child seat and an out-of-positionadult can be a different object than a normally-seated adult. Not allpattern recognition systems are trained systems and not all trainedsystems are neural networks. Other pattern recognition systems are basedon fuzzy logic, sensor fusion, Kalman filters, correlation as well aslinear and non-linear regression. Still other pattern recognitionsystems are hybrids of more than one system such as neural-fuzzysystems.

The use of pattern recognition, or more particularly how it is used, isimportant to some of the inventions disclosed herein. In the above-citedprior art, except the current assignee's, pattern recognition which isbased on training, as exemplified through the use of neural networks, isnot mentioned for use in monitoring the interior passenger compartmentor exterior environments of the vehicle in all of the aspects of theinvention disclosed herein. Thus, the methods used to adapt such systemsto a vehicle are also not mentioned.

A “pattern recognition algorithm” will thus generally mean an algorithmapplying or obtained using any type of pattern recognition system, e.g.,a neural network, sensor fusion, fuzzy logic, etc.

To “identify” as used herein will generally mean to determine that theobject belongs to a particular set or class. The class may be onecontaining, for example, all rear facing child seats, one containing allhuman occupants, or all human occupants not sitting in a rear facingchild seat, or all humans in a certain height or weight range dependingon the purpose of the system. In the case where a particular person isto be recognized, the set or class will contain only a single element,i.e., the person to be recognized. The class may also be one containingall frontal impact airbag-desired crashes into a pole at 20 mph, onecontaining all events where the airbag is not required, or onecontaining all events requiring a triggering of both stages of a dualstage gas generator with a 15 millisecond delay between the triggeringof the first and second stages.

To “ascertain the identity of” as used herein with reference to anobject will generally mean to determine the type or nature of the object(obtain information as to what the object is), i.e., that the object isan adult, an occupied rear-facing child seat, an occupied front-facingchild seat, an unoccupied rear-facing child seat, an unoccupiedfront-facing child seat, a child, a dog, a bag of groceries, a car, atruck, a tree, a pedestrian, a deer etc.

An “object” in a vehicle or an “occupying item” of a seat may be aliving occupant such as a human or a dog, another living organism suchas a plant, or an inanimate object such as a box or bag of groceries oran empty child seat.

A “rear seat” of a vehicle as used herein will generally mean any seatbehind the front seat on which a driver sits. Thus, in minivans or otherlarge vehicles where there are more than two rows of seats, each row ofseats behind the driver is considered a rear seat and thus there may bemore than one “rear seat” in such vehicles. The space behind the frontseat includes any number of such rear seats as well as any trunk spacesor other rear areas such as are present in station wagons.

An “optical image” will generally mean any type of image obtained usingelectromagnetic radiation including visual, infrared, terahertz andradar radiation.

In the description herein on anticipatory sensing, the term“approaching” when used in connection with the mention of an object orvehicle approaching another will usually mean the relative motion of theobject toward the vehicle having the anticipatory sensor system. Thus,in a side impact with a tree, the tree will be considered as approachingthe side of the vehicle and impacting the vehicle. In other words, thecoordinate system used in general will be a coordinate system residingin the target vehicle. The “target” vehicle is the vehicle that is beingimpacted. This convention permits a general description to cover all ofthe cases such as where (i) a moving vehicle impacts into the side of astationary vehicle, (ii) where both vehicles are moving when theyimpact, or (iii) where a vehicle is moving sideways into a stationaryvehicle, tree or wall.

“Out-of-position” as used for an occupant will generally mean that theoccupant, either the driver or a passenger, is sufficiently close to anoccupant protection apparatus (airbag) prior to deployment that he orshe is likely to be more seriously injured by the deployment eventitself than by the accident. It may also mean that the occupant is notpositioned appropriately in order to attain the beneficial, restrainingeffects of the deployment of the airbag. As for the occupant being tooclose to the airbag, this typically occurs when the occupant's head orchest is closer than some distance such as about 5 inches from thedeployment door of the airbag module. The actual distance where airbagdeployment should be suppressed depends on the design of the airbagmodule and is typically farther for the passenger airbag than for thedriver airbag.

“Transducer” or “transceiver” as used herein will generally mean thecombination of a transmitter and a receiver. In some cases, the samedevice will serve both as the transmitter and receiver while in others,two separate devices adjacent to each other will be used. In some cases,a transmitter is not used and in such cases, transducer will mean only areceiver. Transducers include, for example, capacitive, inductive,ultrasonic, electromagnetic (antenna, CCD, CMOS arrays), electric field,weight measuring or sensing devices. In some cases, a transducer maycomprise two parts such as the plates of a capacitor or the antennas ofan electric field sensor. Sometimes, one antenna or plate willcommunicate with several other antennas or plates and thus for thepurposes herein, a transducer will be broadly defined to refer, in mostcases, to any one of the plates of a capacitor or antennas of a fieldsensor and in some other cases, a pair of such plates or antennas willcomprise a transducer as determined by the context in which the term isused.

For the purposes herein, a “neural network” is defined to include allsuch learning systems including cellular neural networks, support vectormachines and other kernel-based learning systems and methods, cellularautomata and all other pattern recognition methods and systems thatlearn. A “combination neural network” as used herein will generallyapply to any combination of two or more neural networks or otherprocessing units as most broadly defined that are either connectedtogether or that analyze all or a portion of the input data. Typically,it is a system wherein the data to be processed is separated intodiscrete values which are then operated on and combined in at least atwo stage process and where the operation performed on the data at eachstage is, in general, different for each discrete value and where theoperation performed is at least determined through a training process.It includes ensemble, modular, cellular neural networks, among others,and support vector machines and combination neural networks.

A “neural computer” is a computer designed to efficiently execute one ormore neural networks primarily in hardware. Thus, it is typically mustfaster than a microprocessor running a neural network algorithm.

A “sensor” as used herein is generally a combination of two transducers(a transmitter and a receiver) or one transducer which can both transmitand receive. In some cases it may refer to a single receiver such as atemperature sensor or passive infrared sensor.

The “headliner” is the trim which provides the interior surface to theroof of the vehicle.

A “sensor system” includes any of the sensors listed above in thedefinition of “sensor” as well as any type of component or assembly ofcomponents that detect, sense or measure something.

An “occupant protection system” or “occupant protection apparatus” isany device, apparatus, system or component which is actuatable ordeployable or includes a component which is actuatable or deployable forthe purpose of attempting to reduce injury to the occupant in the eventof a crash, rollover or other potential injurious event involving avehicle.

An “occupant restraint device” includes any type of device that isdeployable in the event of a crash involving the vehicle for the purposeof protecting an occupant from the effects of the crash and/orminimizing the potential injury to the occupant. Occupant restraintdevices thus include frontal airbags, side airbags, seatbelt tensioners,nets, knee bolsters, side curtain airbags, externally deployable airbagsand the like.

A diagnosis of the “state of the vehicle” means a diagnosis of thecondition of the vehicle with respect to its stability and properrunning and operating condition. Thus, the state of the vehicle could benormal when the vehicle is operating properly on a highway or abnormalwhen, for example, the vehicle is experiencing excessive angularinclination (e.g., two wheels are off the ground and the vehicle isabout to rollover), the vehicle is experiencing a crash, the vehicle isskidding, and other similar situations. A diagnosis of the state of thevehicle could also be an indication that one of the parts of thevehicle, e.g., a component, system or subsystem, is operatingabnormally.

A “part” of the vehicle includes any component, sensor, system orsubsystem of the vehicle such as the steering system, braking system,throttle system, navigation system, airbag system, seatbelt retractor,air bag inflation valve, air bag inflation controller and airbag ventvalve, as well as those listed below in the definitions of “component”and “sensor”.

The crush sensing zone is that portion of the vehicle that has crushedat the time that the crash sensor must trigger deployment of therestraint system.

The term “airbag” is often used to mean all deployable passive passengerprotective devices including airbags, seatbelts with pretensioners anddeployable nets.

The “A-pillar” of a vehicle and specifically of an automobile is definedas the first roof supporting pillar from the front of the vehicle andusually supports the front door. It is also known as the hinge pillar.

The “B-Pillar” is the next roof support pillar rearward from theA-Pillar.

The “C-Pillar” is the final roof support usually at or behind the rearseats

The term “squib” represents the entire class of electrically initiatedpyrotechnic devices capable of releasing sufficient energy to cause avehicle window to break. It is also used to represent the mechanismwhich starts the burning of an initiator which in turn ignites thepropellant within an inflator. Squib generally refers to electricalinitiation while primer is usually used for mechanical initiationhowever these terms are frequently used interchangeably and thus eitherwill mean the device that initiates airbag deployment whether byelectrical or mechanical means.

The term “airbag module” generally connotes a unit having at least oneairbag, a gas generator for producing a gas, an attachment or couplingstructure for attaching the airbag(s) to and in fluid communication withthe gas generator so that gas is directed from the gas generator intothe airbag(s) to inflate the same, an initiator for initiating the gasgenerator in response to a crash of the vehicle for which deployment ofthe airbag is desired and structure for attaching or connecting the unitto the vehicle in a position in which the deploying airbag(s) will beeffective in the passenger compartment of the vehicle. In the instantinvention, the airbag module may also include occupant sensingcomponents, diagnostic and power supply electronics and componentrywhich are either within or proximate to the module housing.

The term “occupant protection device” as used herein generally includesany type of device which is deployable in the event of a crash involvingthe vehicle for the purpose of protecting an occupant from the effectsof the crash and/or minimizing the potential injury to the occupant.Occupant protection devices thus include frontal airbags, side airbags,seatbelt tensioners, knee bolsters, side curtain airbags, deployablenets, externally deployable airbags and the like.

A “composite airbag” is any airbag comprised of a film and a fabric, twoor more films, a film and a net or other combination of two or morematerials or layers such that each material contributes to thestructural or tear properties of the composite. This is in contrast tothe combinations of a film and fabric used previously in neoprene orsilicone coated fabric airbags in that, in the prior art cases, thecoating does not materially effect either the elastic modulus,stiffness, strength or tear resistance of the airbag where in the caseof the composite airbag disclosed herein, the film contributessignificantly to one or more of these properties. Note that the two ormore layers may or may not be joined together including cases where thelayers are joined during an extrusion processing step such as inco-extrusion, by a casting process, progressive coating process, orwhere a film layer is combined with another reinforcing material such asfibers or a woven or molded net in addition to the most common method ofjoining layers by adhesive.

The following definitions related to coatings are generally taken fromU.S. Pat. No. 6,087,016 and U.S. Pat. No. 6,232,389. As used herein, theterm “mixture” or “coating mixture” is interpreted to include trueliquid solutions, as well as colloidal dispersions, suspensions,emulsions and latexes as they are conventionally defined. For example,by “colloidal dispersion or latex”, it is meant any dispersion orsuspension of particles in liquid, the particles being of a size greaterthan molecular scale, e.g., about 0.001 to about 0.1 micron. An emulsiongenerally contains particles of about 0.05 to 1.0 microns, in liquid. A“suspension” generally contains particles of greater than 1.0 micron inliquid.

A “barrier coating mixture” as used herein means a liquid containingdissolved or suspended solids, which is used to apply the solids to asubstrate. A novel aspect of one of the present inventions is that thebarrier coating mixtures provide a better dispersion of platelet fillersin liquid at an unusually low solids content, e.g., between about 1% toabout 30% solids as described in more detail below. According to thisinvention, once the “coating mixture” is dried, it is referred to as a“dried coating” or a “film”. The term “vapor barrier” implies a barrierto a liquid and its vapor. Conventionally, a vapor is the gas inequilibrium with a liquid at atmospheric pressure. For simplicity, asused herein, the term “vapor barrier” can be interpreted to mean abarrier to gases and chemicals as well as traditionally defined vapors,as well as a barrier to moisture, generally water or water vapor.

The term “gas barrier” includes a barrier to oxygen, nitrogen, carbondioxide and other gases. The term “chemical barrier” includes a barrierto the migration or blooming of a molecule from one substrate to anotheror out of one substrate to that substrate's surface.

The term “aspect ratio” is a characteristic of every platelet materialin solid form. Aspect ratio is a lateral dimension of a platelet fillerparticle, e.g., mica flake, divided by the thickness of the platelet.The term “high aspect ratio” refers to a platelet filler whose lateraldimension divided by thickness is greater than 25. The aspect ratio ofany filler is an inherent property of the selected filler. For example,MICROLITE® 963++aqueous vermiculite solution [W. R. Grace] has acharacteristic aspect ratio of about 10,000 or dimensions of 10-30 μm×10Å.

Intercalation is defined as the state of a coating composition in whichpolymer is present between each layer of a platelet filler.Intercalation can be defined by the detection of an X-ray line,indicating a larger spacing between vermiculite layers than in theoriginal mineral. The term “exfoliation” is defined for layered fillersas the complete separation of individual layers of the originalparticle, so that polymer completely surrounds each particle.Preferably, so much polymer is present between each platelet, that theplatelets are randomly spaced. No X-ray line appears because of therandom spacing of exfoliated platelets. In some circumstances, thefiller can exfoliate when dispersed in an aqueous or non-aqueous medium.This would result in a higher aspect ratio than that of a solid particlebefore dispersion.

The term “effective aspect ratio” relates to the behavior of theplatelet filler when incorporated into a binder. The platelet may notexist in a single platelet formation, but in many forms, such as abundle of 10-50 platelets or hundreds of platelets, referred to asagglomerates. If the platelets are not in the single layer form, theaspect ratio of the entire bundle or agglomerate is much lower than thatof the single layer particle. Therefore, the aspect ratio of theparticles in a binder is referred to as an effective aspect ratio. Theeffective aspect ratio is determined by plotting the experimental dataversus theoretical model, such as described by E. L. Cussler et al, J.Membrane Sci., 38:161-174 (1988). A graph of reduction in permeabilityversus the volume % of filler in the binder generates theoretical curvesfor each effective aspect ratio. The graph predicts an effective aspectratio for the experimental data (see FIG. 113).

It is important in the understanding of the effects of the coatings ofthis invention to differentiate between “effective aspect ratio” and“aspect ratio”. The aspect ratio is characteristic of a plateletmaterial in the solid form or one platelet and can be determined bylight scattering techniques or microscopy. The term “effective aspectratio” is much different in that it relates to the behavior of theplatelet when incorporated into a binder. It may no longer be a singleplatelet but instead bundles of platelets referred to as agglomerates.This value is determined using experimental permeability data plottedversus theoretical behavior of the platelet. For example, experimentaldata when plotted versus the theoretical model of the platelet in thebinder [see E. L. Cussler et al, J. Membrane S., 38:161-174 (1988)] isdirectly related to the barrier improvement of the coating throughCussler's theoretical model. Most commercially available fillers haveaspect ratios ranging from 25 up to 10,000. However, the effectiveaspect ratio of these fillers is much lower when incorporated into abinder and is directly related to the barrier improvement due to theplatelet filler, generally resulting in reduced barrier properties. Itis important to distinguish between these terms for barrier coatingscontaining platelet fillers.

Much of the disclosure above and below involving particular barriercoatings is based on U.S. Pat. No. 6,087,016 and U.S. Pat. No.6,232,389. However, the invention is not limited to airbags includingthe barrier coatings described in these patents and encompasses airbagsincluding any comparable barrier coatings and any barrier coatingsencompassed by the claims.

Preferred embodiments of the invention are described below and unlessspecifically noted, it is the applicants' intention that the words andphrases in the specification and claims be given the ordinary andaccustomed meaning to those of ordinary skill in the applicable art(s).If applicants intend any other meaning, they will specifically statethey are applying a special meaning to a word or phrase.

Likewise, applicants' use of the word “function” here is not intended toindicate that the applicants seek to invoke the special provisions of 35U.S.C. §112, sixth paragraph, to define their invention. To thecontrary, if applicants wish to invoke the provisions of 35 U.S.C.§112,sixth paragraph, to define their invention, they will specifically setforth in the claims the phrases “means for” or “step for” and afunction, without also reciting in that phrase any structure, materialor act in support of the function. Moreover, even if applicants invokethe provisions of 35 U.S.C. § 112, sixth paragraph, to define theirinvention, it is the applicants' intention that their inventions not belimited to the specific structure, material or acts that are describedin the preferred embodiments herein. Rather, if applicants claim hisinventions by specifically invoking the provisions of 35 U.S.C. § 112,sixth paragraph, it is nonetheless their intention to cover and includeany and all structure, materials or acts that perform the claimedfunction, along with any and all known or later developed equivalentstructures, materials or acts for performing the claimed function.

6 References

-   1. Breed, D. S., Castelli, V. “Problems in Design and Engineering of    Air Bag Systems”, Society of Automotive Engineers (SAE) paper No.    880724, 1988.-   2. Breed, D. S., Castelli, V. “Trends in Sensing Frontal Impacts”,    SAE paper No. 890750, 1989.-   3. Castelli, V., Breed, D. S. “Trends in Sensing Side Impacts”, SAE    paper No. 890603, 1989.-   4. Breed, D. S., Castelli, V. and Shokoohi, F. “Are Barrier Crashes    Sufficient for Evaluating Air Bag Sensor Performance?”, SAE paper    No. 900548, 1990.-   5. Breed, D. S., Sanders, W. T. and Castelli, V. “A Critique of    Single Point Crash Sensing”, SAE paper No. 920124, 1992.-   6. Breed, D. S., Sanders, W. T. and Castelli, V. “Performance of a    Crush Sensor for Use with Automobile airbag Systems”, SAE paper No.    920122, 1992.-   7. Shokoohi, F., Sanders, W. T., Castelli, V., and Breed, D. S.    “Cross Axis Specifications For Crash Sensors”, Automotive    Technologies International Report, ATI 12004, 1991. SAE paper No.    930651, 1993.-   8. Breed, D. S., Sanders, W. T. and Castelli, V. “A Complete Frontal    Crash Sensor System—I”, SAE paper No. 930650, 1993.-   9. Breed, D. S. and Sanders, W. T. “Using Vehicle Deformation to    Sense Crashes”, Presented at the International Body and Engineering    Conference, Detroit Mich., 1993.-   10. Breed, D. S., Sanders, W. T. and Castelli, V., “A complete    Frontal Crash Sensor System—II”, Proceedings Enhanced Safety of    Vehicles Conference, Munich, 1994, Published by the U.S. Department    of Transportation, National Highway Traffic Safety Administration,    Washington, D.C.-   11. Breed, D. S., Sanders, W. T. and Castelli, V., “Sensing Side    Impacts”, SAE paper No. 940561, 1994.-   12. Breed, D. S., “Side Impact Airbag System Technology”, Presented    at the International Body and Engineering Conference, Detroit Mich.,    1994.-   13. Breed, D. S., “A Smart Airbag System”, Presented at the 16^(th)    International Technical Conference on the Enhanced Safety of    Vehicles, Windsor, Canada, Paper Number 98 S5 O 13, 1998.-   14. Breed, D. S. “How Airbags Work” Presented at the Canadian    Association of Road Safety Professionals International Conference on    Airbags and Seat Belts, Oct. 19-20, 1992, Montreal, Quebec, Canada

OBJECTS AND SUMMARY OF THE INVENTION

1 Crash Sensors

This invention relates to the use of crush zone mounted sensors,sometimes called satellite sensors, in a smart airbag system. Thesesensors may comprise one or more micromachined or piezo-electricaccelerometers, one or more gyroscopes, associated electronic circuitry,and/or one or more electromechanical sensors. One focus of thisinvention is the part of smart airbag systems that makes use ofdistributed sensors mounted on the periphery of the vehicle to senseimpacts to the front, side or rear of the vehicle and to use informationfrom such sensors to permit a more precise assessment of the crashinjury potential and to permit the tailoring of the deployment of one ormore airbags to optimize occupant protection.

Principle objects of some of the disclosed inventions, include:

1) To provide a sensor system that will sense all airbag-desired crashesinvolving the either the front, rear or a side of the vehicle whereinthe sensors are mounted in the crush zones of the vehicle.

2) To provide an electronic sensor for mounting in the vehicle crushzone for frontal, side or rear impacts.

3) To improve crash sensing and crash severity forecasting by combiningelectronic crush zone-mounted sensors with electronic non-crush zone (orpassenger compartment) mounted electronic sensors.

4) To improve the determination of the state of the vehicle by usingdistributed electronic crush zone-mounted sensors.

5) To provide a sensor which is much longer than it is wide or thickthus permitting it to sense crashes over a large area while occupying arelatively small space.

6) To provide a sensor that can be easily shaped so to be properlyplaced in the crush zone across the entire front, side or rear of thevehicle

7) To provide a crush sensor where the rate of deformation required totrigger the sensor can be measured along the length of the sensor.

8) To provide a sensor to be used in conjunction with an electronicpassenger compartment-mounted sensor which will trigger on all of theairbag desired crashes which are missed by the electronic passengercompartment-mounted sensor alone for either frontal, side or rearimpacts.

9) To provide a simple and convenient sensor system consisting of asingle discriminating sensor mounted in crush zones and one or morearming sensors mounted in the passenger compartment for frontal, sideand/or rear impacts.

10) To provide a crush velocity change crash sensor which functions whena portion of the vehicle where the sensor is mounted is displaced,deformed or otherwise bends or buckles.

11) To provide a hermetically sealed crush velocity sensing crashsensor.

12) To provide a small, inexpensive, yet highly reliable crash velocitychange sensor.

13) To provide an arrangement for a vehicle including a crushzone-mounted discriminating sensor (which provides information about thereaction of the crush zone to a crash, such as the crush of the crushzone, the velocity change of the crush zone resulting from the crash andthe acceleration of the crush zone resulting from the crash) used inconjunction with a passenger compartment-mounted discriminating sensorto permit a better discrimination between airbag desired and not desiredcrashes such as animal impacts.

14) To provide an arrangement for a vehicle including a crushzone-mounted discriminating sensor as input to an electronicpassenger-compartment discriminating sensor module to permit a change inthe sensor algorithm, or triggering parameters, based of the output ofthe crush zone discriminating sensor to improve the performance of thesensor system.

15) To control the deployment of occupant restraint systems bymonitoring the patterns of signals emitted from the vehicle sensors and,through the use of pattern recognition technology, forecasting theexistence and severity of a vehicle crash.

16) To provide a new and improved on-board vehicle diagnostic moduleutilizing pattern recognition technologies which are trained todifferentiate normal component behavior from abnormal componentbehavior.

17) To provide a diagnostic module that determines whether a vehicle isexperiencing a crash based on a time series of data from a single sensoror from multiple sensors that contain a pattern indicative of theoperating status of the sensors.

18) To simultaneously monitor several sensors, primarily accelerometers,gyroscopes and strain gages, to determine the state of the vehicle andoptionally its occupants and to determine that a vehicle is having anaccident, for example. If this is so, then the same system of sensorscan monitor the early stages of a crash to make an assessment of theseverity of the crash and what occupant protection systems should bedeployed and how such occupant protection systems should be deployed.

19) To apply trained pattern recognition techniques using multiplesensors to provide an early prediction of the existence and severity ofan accident.

20) To utilize pattern recognition techniques and the output frommultiple sensors to determine at an early stage that a vehicle rollovermight occur to deploy side head protection airbags to reduce theinjuries.

In order to achieve these objects and others, a vehicle with an occupantsafety system for use in a crash involving the vehicle in accordancewith the invention comprises a deployable occupant protection device,acceleration sensing device for measuring acceleration of the vehicle(such as a tri-axial accelerometer or part of an IMU), at least onegyroscope for measuring angular motion of the vehicle and a processorcoupled to the acceleration sensing device and the gyroscope(s) forreceiving the measured acceleration of the vehicle and the measuredangular motion of the vehicle. The processor determines whetherdeployment of the occupant protection device is beneficial, and if so,generates a signal to initiate deployment of the occupant protectiondevice. The processor may embody a pattern recognition technique foranalyzing the measured acceleration and angular motion of the vehicleand determine whether deployment of the occupant protection device isbeneficial. For example, the pattern recognition technique may be aneural network trained to determine whether the vehicle is experiencinga crash based on the measured acceleration of the vehicle and themeasured angular motion of the vehicle.

Additional enhancements to the occupant safety system include anoccupant position sensor for monitoring position of an occupant to beprotected by the occupant protection device. In this case, the processoris coupled to the occupant position sensor and determines whetherdeployment of the occupant protection device is beneficial based on themeasured acceleration of the vehicle, the measured angular motion of thevehicle and the position of the occupant. An occupant weight sensor formeasuring weight of an occupant to be protected by the occupantprotection device, a wheel speed sensor for measuring the speed of awheel of the vehicle and/or an engine speed sensor for measuring thespeed of an engine of the vehicle may be provided instead of or inaddition to the occupant position sensor. In each case, the processor iscoupled to the additional sensor(s) and determines whether deployment ofthe occupant protection device is beneficial based on the parametermeasured by the additional sensor(s).

The occupant protection device may be an airbag inflatable with a gas,in which case, a control module is arranged to control how much gas isto be generated for inflation of the airbag, how fast the gas is to begenerated, how much gas should be directed into the airbag, how much gasshould be directed to an atmosphere and/or how much gas should bepermitted to exhaust from the airbag. The control module is coupled tothe processor and the processor determines settings for the controlmodule based on the measured acceleration of the vehicle and themeasured angular motion of the vehicle.

A method for controlling deployment of an occupant protection device ina vehicle in accordance with the invention entails measuringacceleration of the vehicle, measuring angular motion of the vehicle bymeans of at least one gyroscope, determining whether deployment of theoccupant protection device is beneficial based on the measuredacceleration and angular motion of the vehicle and when deployment ofthe occupant protection device is determined to be beneficial,generating a signal to initiate deployment of the occupant protectiondevice. The same enhancements described above for the safety system canbe used in the method as well.

Another embodiment of a vehicle with an occupant safety system for usein a rollover crash involving the vehicle includes a deployable occupantprotection device, a sensor for measuring angular motion of the vehicleand a processor coupled to the sensor and the occupant protection devicefor receiving the measured angular motion and determining whether theangular motion is indicative of rollover of the vehicle. If so, theprocessor generates a signal to initiate deployment of the occupantprotection device. The sensor may comprise an IMU. The same enhancementsdescribed above for the first embodiment of the safety system can beused in this embodiment as well.

A related method for controlling deployment of an occupant protectiondevice in a vehicle experiencing a rollover entails measuring angularmotion of the vehicle, determining whether the measured angular motionis indicative of a rollover, if so, determining whether deployment ofthe occupant protection device is beneficial based on the measuredangular motion of the vehicle, and when deployment of the occupantprotection device is determined to be beneficial, generating a signal toinitiate deployment of the occupant protection device. The sameenhancements described above for the first embodiment of the safetysystem can be used in this method as well.

Also, to achieve one or more of the above objects, a crash sensorarrangement for determining whether the crash involving the vehiclerequires deployment of the occupant restraint device includes a firstelectronic crash sensor mounted in the crush zone of the vehicle tomeasure a reaction of the crush zone to the crash and to output a signalrepresentative of the measurements and a processor coupled to the firstsensor to process the signal from the first electronic sensor anddetermine whether the occupant restraint device should be deployed basedin part thereon. The reaction of the crush zone to the crash may bedisplacement of the crush zone during the crash relative to anon-crushed part of the vehicle, a velocity change of the crush zoneduring the crash and/or acceleration of the crush zone during the crash.The first electronic sensor may include an accelerometer, a gyroscope oran elongate member arranged to sense the reaction of the crush zone overa substantial part of the front, side or rear of the vehicle.

Optionally, a second electronic crash sensor is mounted outside of thecrush zone of the vehicle to measure a reaction of the vehicle by meansother than crush of the crush zone of the vehicle. In this case, bothelectronic sensors input signals to the processor which is programmed todetermine whether the occupant restraint device should be deployed usingan algorithm and data from the first and/or second electronic sensors.The reaction of the vehicle to the crash is relative displacement of thevehicle during the crash relative to a coordinate system moving at apre-crash velocity, a velocity change of the vehicle during the crashand/or acceleration of the vehicle during the crash.

The second electronic sensor may be mounted in association with thepassenger compartment of the vehicle. The first and second electronicsensors may have different sensitivities to crashes and optionally, thesecond electronic sensor is more sensitive to crashes than the firstsensor.

In another embodiment, a crash sensor arrangement in accordance with theinvention comprises a processor, a first electronic discriminating crashsensor mounted outside of the crush zone of the vehicle to measure thereaction of the vehicle to the crash by means other than crush of thecrush zone of the vehicle and to provide information about the measuredreaction to the processor, and a second electronic crash sensor mountedin the crush zone of the vehicle. The second electronic sensor providesinformation about a reaction of the crush zone to the crash to theprocessor. The processor receives the information about the reaction ofthe vehicle to the crash from the first electronic sensor and thereaction of crush zone of the vehicle from the second electronic sensorand determines based on the information whether the occupant restraintdevice should be deployed.

Some typical reactions of the crush zone which are measured by thesecond electronic discriminating crash sensor are the crush of thevehicle crush zone, displacement of the vehicle crush zone, accelerationof the vehicle crush zone, or velocity change of the vehicle crush zone.

The processor may embody a pattern recognition algorithm to determinewhether to deploy the occupant restraint device.

The first electronic sensor may measure the reaction of the entirevehicle or a part of the vehicle other than the crush zone of thevehicle to the crash such as acceleration of the vehicle and/or a changein velocity of the vehicle.

The sensors may be coupled to one another in series such that the signalto deploy the occupant restraint device is generated only when the firstand second sensors are both triggered. In another embodiment, the firstsensor receives a signal indicative of triggering of the second sensor,considers whether to modify its triggering algorithm, triggeringcriteria and/or sensitivity based on the triggering or velocity changeof the second sensor and if so, modifies the triggering algorithm,criteria or sensitivity. If the first sensor is an electronic sensorwhich triggers based on a change in velocity and/or acceleration of thevehicle (or functions thereof), the velocity change and/or acceleration(or functions thereof) required for triggering may be modified based onthe triggering of the second sensor. It should be noted though that suchmodification is not required in the event the velocity change is alreadyappropriate.

The second discriminating sensor mounted in the crush zone may be a tapecrush sensor including a tape switch comprising a pair of electricallyconductive members spaced apart from one another prior to crush of thevehicle and which are designed to come into contact with one anotherupon crush of the vehicle of a specific magnitude. The tape crush sensorcan include structure for reducing the sensitivity of the tape crushsensor, such as an encapsulating member around the sensor. The firstdiscriminating sensor may also be a ball-in-tube sensor or an electronicsensor.

A method for determining whether the crash involving the vehiclerequires deployment of an occupant restraint device, comprises mountingan electronic crash sensor in the crush zone of the vehicle, theelectronic sensor measuring the reaction of the crush zone of thevehicle to the crash, and enabling deployment of the occupant restraintdevice based of an analysis of the measurements of the electronicsensor.

Optionally, a second electronic crash sensor is mounted outside of thecrush zone of the vehicle to measure a reaction of the vehicle to thecrash by means other than crush of the crush zone of the vehicle, anddeployment of the occupant restraint device enabled based on an analysisof the measurements of the first and second electronic sensors. In thiscase, a signal indicative of the measurements of the first electronicsensor and a signal indicative of the measurements of the secondelectronic sensor are directed to a processor, it is considered thereinwhether the conditions for deploying the occupant restraint device aremet by the measurements from the first electronic sensor or themeasurements from the second electronic sensor or a combination of themeasurements from both electronic sensors, and the occupant restraintdevice is deployed when the conditions are met.

The second electronic sensor may measure a change in velocity of thevehicle and/or acceleration of the vehicle. In this case, it is possibleto direct a signal indicative of triggering of the first electronicsensor to the processor, direct a signal indicative of triggering of thesecond electronic sensor to the processor, consider whether the measuredvelocity change and/or acceleration of the second electronic sensor inconjunction with the measurements of the first electronic sensor aresufficient to require deploying the occupant restraint device, and ifso, deploy the occupant restraint device.

Another method for determining whether a crash involving a vehiclerequires deployment of an occupant restraint device comprises mounting afirst electronic crash sensor outside of the crush zone of the vehicleto measure the reaction of the vehicle to a crash by means other thancrush of the crush zone of the vehicle, mounting a second electroniccrash sensor in the crush zone of the vehicle to generate informationabout a reaction of the crush zone of the vehicle to a crash, providingthe information about the reaction of the crush zone of the vehicle tothe crash from the second sensor and the first sensor to a processor,and controlling deployment of the occupant restraint device via thefirst electronic sensor based on the information about the reaction ofthe crush zone of the vehicle to the crash provided by the secondelectronic sensor.

Control of the deployment of the occupant restraint device via the firstelectronic sensor may entail considering whether an algorithm orparameters which determine deploying of the occupant restraint device bythe first electronic sensor should be modified based on the informationabout crush of the vehicle provided by the second electronic sensor, andif so modifying the algorithm or parameters.

Control of the deployment of the occupant restraint device may alsoentail considering whether the acceleration and/or velocity changerequired for deployment of the occupant restraint device by the firstelectronic sensor should be modified based on the information aboutcrush of the vehicle provided by the second sensor, and if so, modifyingthe requirements.

Note, in some cases, when the non-crush zone sensor is not present ormalfunctioning, or when there is insufficient signal at the non-crushzone sensor mounting location, the processor may initiate triggeringbased on the acceleration signal of the crush zone mounted accelerometeralone.

2 Inflators

Other principle objects and advantages of disclosed inventions are:

1) To provide a new and improved electrical wiring system for couplingsensors and actuators in a motor vehicle in order to reduce the amountof wire in the motor vehicle and improve system reliability.

2) To provide a vehicle safety wiring system including a networkcomprising various safety devices such as crash sensors and airbaginflator igniters.

3) To associate much of the airbag electronics with the airbag module soas to improve the reliability of the system.

4) To provide a new and improved airbag module which is designed so thatif an occupant is out-of-position and/or leaning against the module, themodule will still enable deployment of the airbag to protect theoccupant.

5) To provide a new and improved airbag module in which a more efficientaspirating system is used, i.e., one having a larger pumping ratio.

6) To permit the deployment of both the frontal and side airbags duringa primarily frontal crash to reduce the probability of injury to theoccupants through impacts with the passenger compartment.

7) To provide a long, thin airbag module which can be convenientlymounted on the ceiling or almost any other surface of the vehicle forthe protection of vehicle occupants in frontal collisions.

8) To provide a highly efficient airbag module that uses the minimumamount of propellant.

9) To provide a rapidly deploying airbag module causing minimal injuryto out-of-position occupants.

10) To provide an airbag module where a single module can be used toprotect both a front and a rear passenger of the vehicle in sideimpacts, as well as frontal and rear impacts to the extent that suchprotection is deemed beneficial.

11) To provide a cover system for an airbag module which is easilyreleased thereby reducing the risk of deployment-induced injuries to thevehicle occupants.

12) To provide an airbag module which can be conveniently mounted on theinstrument panel, or knee bolster support structure, to provide knee andleg protection for the vehicle occupant as well as for an occupant, suchas a child, lying on the seat.

13) To provide a driver protection airbag system for use with vehicleshaving servo power steering and thereby promote the elimination of themassive steering column and steering wheel.

14) To provide an airbag module which is displaced from its mountingsurface during the initial stage of airbag deployment to thereby openingaspirating channels.

15) To provide a highly efficient aspirated airbag module.

16) To provide a long thin airbag module where the module isapproximately the same length as the inflated airbag thereby simplifyingthe folding, and unfolding during deployment, of the airbag and permitmore rapid airbag deployment.

17) To provide an airbag module which is easily replaced when thevehicle is repaired after an accident.

18) To provide a ceiling-mounted airbag module for protection offront-seated occupants and rear-seated occupants.

19) To provide an aspirated airbag system where the aspiration inletports are also used as the venting ports for the airbag, including anautomatic adjustment system to reduce the vent area, thereby simplifyingthe airbag design by removing the requirement for vents within theairbag material.

20) To provide an inflator design wherein the propellant is a singlesolid material attached to the inside of the inflator housing therebysimplifying the inflator design and providing a definable burningsurface.

21) To provide a method of ignition of a propellant through a coatingplaced on the surface of a propellant containing an igniter materialsuch as BKNO₃.

22) To provide a thin airbag module that can be mounted substantially ona surface of the passenger compartment such as the ceiling, instrumentpanel, or seat back without penetrating deeply within the surface.

23) To provide for a thin airbag module which can be made to conform toa curved surface.

24) To provide an inflator design wherein the propellant is a liquidsubstantially filling the inside of the inflator housing therebysimplifying the inflator design and providing a definable burningsurface.

25) To provide new and improved methods and apparatus which permit theuse of propellants in inflators for airbag system which otherwise wouldnot be usable due to their toxicity.

26) To provide an airbag system where multiple airbags are deployed in avehicle and where the gas used to inflate the airbags is toxic to humansbut is removed from the passenger compartment before it causes injury tothe occupants, thereby permitting the use of heretofore unusable toxicpropellants.

27) To provide a system to relieve the excess pressure generated by thedeployment of multiple airbags thereby preventing the doors from beinginadvertently opened by this excess pressure.

28) To provide a method of breaking a window in the vehicle to relievethe excess pressure and create a path for toxic gases and excesspressure to escape.

29) To provide a system which only deploys those airbags in the vehiclewhich are likely to help prevent occupants from being injured, therebyminimizing the total number of airbags deployed during a crash.

30) To provide an airbag deployment delay system within one or more ofthe airbag modules in order to reduce the peak pressure and noise withinthe vehicle.

31) To permit the use of large knee protection airbags which helpsreduce injuries to an occupant who is lying on a seat during anaccident.

32) To provide protection for an occupant from the impact with variousvehicle roof support pillars in the event of a frontal angular impact,or other impact, by providing side protection airbags which are deployedalong with the frontal impact protection airbags through a method ofrelieving the excess pressure caused by the deployment of multipleairbags.

33) To provide a system that permits more than two airbags to bedeployed during a single crash event.

In order to achieve at least some of the objects above and others, amethod for inflating an airbag in a vehicle to protect an occupant inthe event of a crash involving the vehicle comprises arranging aninflator having a propellant in the vehicle, igniting the propellantafter determination of a crash involving the vehicle to generate gastherefrom, directing the gas into an airbag, and controlling pressure inthe airbag based on the occupant by varying the flow of gas into theairbag. Variation in the flow of gas into the airbag may be obtained byvarying a flow of aspirating gas into a mixing chamber in which theaspirating gas mixes with gas generated from the propellant. Forexample, if the inflator has at least one variable passage through whichthe gas flows in a path toward the airbag, the cross-sectional area ofthe at least one passage may be controlled based on the pressure in themixing chamber.

The inflator may be arranged in a housing having a cover exposed to apassenger compartment of the vehicle, in which case, the pressure in theairbag can be controlled based on the occupant's position relative tothe cover or airbag, e.g., to prevent injury to the occupant when theoccupant is leaning on the cover. Pressure in the airbag may also becontrolled based on the occupant by forming variable gas flow ports,e.g., between the inflator and the airbag, with the size of the portsbeing dependent on pressure exerted by the occupant against the airbag.Pressure in the airbag may also be controlled by opening aspiratingports when the occupant is leaning on the cover such that gas generatedfrom the propellant flows out through the aspirating ports and not intothe airbag when the occupant is leaning on the cover.

Another method for controlling combustion of a propellant which producesgas when burning, the gas being used to inflate an airbag on a vehicle,entails housing the propellant in a chamber on the vehicle, providing atleast one exit conduit in flow communication with the chamber, andadjusting the cross-sectional area of the exit conduit(s) duringcombustion of the propellant to thereby continuously control thepressure in the chamber and thus the rate of combustion of thepropellant. The chamber may be defined by a gas generator mounted to abase to thereby define a nozzle between the gas generator and the basewhich constitutes an exit conduit. In this case, the cross-sectionalarea of the nozzle may be adjusted by mounting the gas generator to thebase via an elastic or flexible supporting structure which holds the gasgenerator against the base. When the gas generator moves apart from thebase, e.g., when pressure in the chamber exerts a force greater than theforce provided by the supporting structure, it causes an increase in thecross-sectional area of the nozzle. Nevertheless, a minimumcross-sectional area of the nozzle can be maintained by arrangingsupports between a surface of the gas generator facing the base and thebase. Alternatively, the cross-sectional area of the nozzle is adjustedby mounting the gas generator to the base via a deformable supportingstructure.

A system for controlling combustion of a propellant which produces gaswhen burning, the gas being used to inflate an airbag on a vehiclecomprises a housing and an inflator including a chamber having apropellant which generates gas upon burning. The inflator is mounted tothe housing to define at least part of at least one exit conduittherebetween in flow communication with the chamber and through whichgas generated from the propellant flows into the airbag and such thatthe exit conduit is capable of having an adjustable cross-sectional areaduring combustion of the propellant to thereby continuously control thepressure in the chamber and thus the rate of combustion of thepropellant. The cross-sectional area of the exit conduit(s) may becontrolled based on the pressure in the chamber.

An elastic or flexible supporting structure for mounting the inflator tothe housing and loading the inflator toward the housing may be provided.The cross-sectional area of the exit conduit(s) could then be adjustablebased on pressure differences between a pressure in the chamber and apressure provided by the supporting structure. The support structure maybe arranged between a surface of the inflator facing the housing and thehousing for maintaining a minimum cross-sectional area of the exitconduit(s). A deformable supporting structure for mounting the inflatorto the housing such that the cross-sectional area of the exit conduit(s)is adjustable upon deformation of the supporting structure can also beprovided. The housing can define at least one variable gas flow portwhich enables gas flow from an interior of the housing to an exterior ofthe housing. The gas flow port enables gas to flow into a mixing chamberdefined by the housing and combine with gas from outside of the housingand gas generated from the propellant and flowing through the exitconduit(s) which then flows out of the housing into the airbag. A covermay be releasably mounted to the housing, in which case, the gas flowport(s) is defined between the cover and a remaining part of thehousing. The cross-sectional area of each exit conduit may be controlledbased on the pressure in the mixing chamber.

An occupant protection system for protecting an occupant in a vehicle inthe event of an accident involving the vehicle comprises at least oneairbag arranged to deploy into a passenger compartment of the vehicle,an inflator system for inflating the at least one airbag and comprisinga housing and an inflator including a chamber having a propellant whichgenerates gas upon burning, the inflator being mounted to the housing todefine at least one exit conduit in flow communication with the chamberand through which gas generated from the propellant flows to inflate theairbag(s), each exit conduit having an adjustable cross-sectional area,and an initiation device arranged to initiate burning of the propellantin response to an accident involving the vehicle such that upon burningof the propellant, gas is generated and flows through the exitconduit(s) into the airbag(s) to inflate it. The variations in thehousing, exit conduit(s), cover, and support structure described abovecan be use din this embodiment as well.

A module for inflating an airbag with gas in accordance with oneembodiment of the invention comprises an elongate housing, an elongateblock of propellant arranged in the housing and generating gas whenburning and preferably, igniter material arranged on the propellant. Theigniter material is substantially coextensive with the propellant in alongitudinal direction such that upon ignition of the igniter material,the propellant begins to burn across its entire length. This isbeneficial as the pressure generated by the gas may be substantiallyuniform provided the propellant is uniformly distributed andhomogeneous. The igniter material may be arranged on portions of thepropellant not in contact with the housing such that the propellant iscompletely enclosed by the housing and igniter material, i.e., notexposed to the ambient atmosphere.

The propellant may have different forms, shapes and dimensions. Forexample, the propellant may have a substantially uniform cross-sectionalshape in a longitudinal direction thereof. The propellant and ignitermaterial, when present, may have a length in the longitudinal directionexceeding ten times their width or thickness in a direction transverseto the longitudinal direction.

The housing typically includes an opening through which gas flows toinflate the airbag, which opening is preferably elongate and oriented inthe same direction as the propellant, possibly coextensive with thepropellant. An elongate screen is optionally arranged adjacent theopening and opposite the propellant and igniter material when present.The housing may include an elongate wall opposite the opening wherebythe propellant is affixed to this wall and the igniter material, whenpresent, is arranged between the propellant and the opening such thatupon ignition of the igniter material, the propellant burns in adirection toward the wall.

Another embodiment of the inflator module comprises an elongate housing,an elongate block of propellant arranged in the housing and generatinggas when burning and optional igniter material arranged on portions ofthe propellant not in contact with the housing such that the propellantis completely enclosed by the housing and the igniter material. Thevariations to the propellant, igniter material and housing describedabove can be applied in this embodiment.

Another embodiment of the inflator module comprises an elongate housingincluding an elongate bottom wall, a pair of opposed longitudinallyextending walls connected to the bottom wall and opposed lateral endwalls connected to the bottom wall to thereby define a reaction chamberbetween the bottom wall, the longitudinally extending walls and thelateral walls. An elongate block of propellant is arranged in thereaction chamber and generates gas when burning. The propellant isarranged along substantially the entire length of the longitudinallyextending walls.

Igniter material is preferably arranged on the propellant substantiallycoextensive with the propellant in a longitudinal direction such thatupon ignition of the igniter material, the propellant begins to burnacross its entire length. The igniter material may be arranged onportions of the propellant not in contact with the bottom wall, thelongitudinally extending walls and the lateral walls such that thepropellant is completely enclosed by the housing and the ignitermaterial. Other variations of the propellant, igniter material andhousing as described above may be incorporated in this embodiment.

An embodiment of an inflator system comprises an elongate block ofpropellant and a layer of igniter material arranged on the propellantand substantially coextensive with the propellant in a longitudinaldirection such that upon ignition of the igniter material, thepropellant begins to burn across its entire length.

Several airbag modules are also encompassed with the scope of theinvention and may include any of the forms of the inflator modules andinflator system described above. Such airbag modules usuallyadditionally include an airbag housing, at least one airbag situated inthe airbag housing which also houses the inflator module, an initiatorfor initiating the inflator module to produce gas in response to thecrash of the vehicle and a cover for releasably retaining the airbag(s)in the airbag housing.

A vehicle including any of the inflator modules, inflator systems orairbag modules described above is also encompassed within the scope ofthe invention. In one particular embodiment, the airbag module ismounted along a side of the vehicle such that the airbag(s) in theairbag module inflates along the side of the vehicle. This is commonlyreferred to as a side curtain airbag in that it provides a curtain alongthe side of the vehicle. If the airbag module includes a single airbag,the airbag may be arranged to extend from a location in front of aB-pillar of the vehicle to a location behind the B-pillar such that theairbag is restrained by the B-pillar upon inflation. The airbag modulecan be mounted to a ceiling of the vehicle, adjacent to and slightlyaway from the side of the vehicle.

3 Airbags

Other objects and advantages of disclosed inventions include, toprovide:

1) an airbag that can be manufactured without the use of sewing or othermanually intensive operations;

2) an airbag that is considerably lighter and smaller, when folded inthe inoperative condition, than current fabric airbags;

3) a driver airbag that does not require the use of tethers;

4) a driver side airbag module, which does not rotate with the steeringwheel;

5) a driver side airbag having an arbitrary shape;

6) an airbag design to prevent the driver from sliding off the airbag;

7) an airbag that has been optimized to substantially equalize thestresses in the material thereof;

8) a substantially conventional driver fabric airbag which can bemanufactured without the use of tethers;

9) an airbag that can be manufactured using a low cost blow molding orsimilar technology;

10) an airbag that has been optimized to substantially equalize thestresses in the material thereof,

11) a very low cost airbag, with respect to the fabrication thereof;

12) a method of manufacturing an airbag permitting any desired shapeairbag to be manufactured from flat panels;

13) an airbag where at least one layer is made from a thermoplasticelastomer which is substantially lighter than conventional fabricairbags;

14) a very low cost airbag, with respect to the fabrication thereof;

15) a method of manufacturing an airbag permitting any desired shapeairbag to be manufactured from flat panels;

16) an airbag where at least one layer is made from a thermoplasticelastomer which is substantially lighter than conventional fabricairbags;

17) an airbag system that automatically adjusts to the presence of achild seat;

18) thin film airbags used in a manner that eliminates the catastrophicbursting of the film in the event of an inadvertent puncture;

19) an airbag module utilizing the combination of an airbag madesubstantially of film and a pyrotechnically opening deployment door;

20) an airbag system that comprises a plurality of airbags;

21) a method of reducing the injury potential to an out-of-positionoccupant from the deploying airbag;

22) an airbag system which exhausts back through the inflator structurethereby eliminating the need for vent holes in the airbag;

23) a method of containing a plurality of airbags;

24) an airbag system for the protection of an occupant whichautomatically adjusts to the occupant's seating position;

25) a simple construction method for an airbag composed of severalairbags;

26) a method of containing a plurality of airbags through the use of anet structure;

27) a method to retain gas in an airbag for a substantial period of timeuntil it is impacted by an occupant;

28) a simple construction method for an airbag composed of severalairbags;

29) an airbag having a plurality of interconnected gas-receivingcompartments;

30) a method to retain gas in an airbag for a substantial period of timeuntil it is impacted by an occupant;

31) a method to minimize the total amount of gas and contaminantsproduced by all of the inflators in the vehicle;

32) an airbag having a plurality of interconnected gas-receivingcompartments;

33) an airbag designed to inflate in the passenger compartment alongsidea side door of the vehicle;

34) an airbag designed to inflate in the passenger compartment acrossthe front of the vehicle;

35) an airbag which provides front-to-side coverage for a front-seatedvehicle occupant that would prevent the occupant from impacting theA-pillar in a crash;

36) a method to enable the implementation of driver side airbags forvehicles with a steep steering column angle, which is unsuitable forconventional airbag modules attached to the steering wheel;

37) the flexibility in the orientation of the sensor, the airbag, andthe steering column;

38) a method to implement an airbag on a soft steering wheel or column,which will align the bag in contact with the occupant according to theforces exerted by the occupant, and to provide a steering wheel assemblywith such an airbag;

39) a method to design airbag systems independent of the steering wheeland the column responses for vehicles that need an airbag module notmoving with the steering wheel and column, and to provide steering wheelassemblies with airbag systems designed as such;

40) a method to direct the exhaust gases of an airbag away from theoccupant or the passenger compartment;

41) a method to control the vent hole of an airbag system so that theairbag can be retained inflated for an extended period;

42) a method to use an aspirated airbag inflator system for the driverside of a vehicle; and

43) a better viewing for the driver to the dashboard or the instrumentpanel.

In order to achieve at least some of these objects, a steering wheelassembly for a vehicle in accordance with the invention includes asteering column including an inner shaft adapted to be attached to afixed part of the vehicle and an outer shaft arranged around the innershaft and rotatable relative to the inner shaft, the outer shaft beingconnected with a steering mechanism which causes turning of tires of thevehicle, a steering wheel connected to and for rotation with the outershaft and an airbag module including an airbag connected to the innershaft such that the airbag module does not rotate upon rotation of theouter shaft and the steering wheel. The airbag is thus stationaryrelative to the steering wheel and as a result, its shape is notconstrained by any limitations which arise when the airbag must rotatealong with the steering wheel as in conventional steering wheel-mountedairbag systems.

A supporting bracket may be provided for mounting the steering column tothe vehicle, and includes a passage through which the inner and outershafts pass. Bearings rotatably support the outer shaft on thesupporting bracket. Additional bearings may also be provided between theinner and outer shafts for rotatably supporting the outer shaft on theinner shaft. The steering wheel may be provided with a central cavitycentered about a rotation axis thereof with the airbag module beingarranged in the cavity.

In a related embodiment of a vehicle, the vehicle includes a steeringmechanism which causes turning of the tire(s) of the vehicle, a steeringcolumn including an inner shaft attached to a stationary part of thevehicle chassis and an outer shaft arranged around the inner shaft andbeing rotatable relative to the inner shaft, the outer shaft beingconnected to the steering mechanism, a steering wheel connected to andfor rotation with the outer shaft, and an airbag module including anairbag connected to the inner shaft such that the airbag module does notrotate upon rotation of the outer shaft and the steering wheel. The samemodifications described above can be applied in this embodiment as well.

Another embodiment of a vehicle in accordance with the inventionincludes a dashboard, a windshield, a firewall arranged behind thedashboard, a steering column projecting away from the dashboard, asteering wheel mounted to the steering column, and an occupantprotection system for protecting a driver of the vehicle in front of thesteering wheel. The occupant protection system includes an airbag modulearranged at least partially in the dashboard and which includes anairbag arranged to deploy between a ceiling of a passenger compartmentof the vehicle, the steering wheel, the dashboard and the windshield.The airbag is arranged in or on the dashboard to deploy in a directionat least partially upward from an upper surface of the dashboard andrearward over the steering wheel into a position to protect the driverfrom injury in the event of a crash. A mechanism may be provided toselectively enable movement of the steering wheel in a direction towardthe dashboard and away from the driver in the event of a crash involvingthe vehicle to thereby provide additional space for deployment of theairbag. To this end, a crash sensor may be provided to sense animpending or actual crash involving the vehicle and direct the mechanismto allow movement of the steering wheel. One embodiment of such amechanism comprises one or more releasable pins having a first positionlocking the steering column in a fixed position and a second, releasedposition enabling movement of the steering column and thus movement ofthe steering wheel toward the dashboard.

In another embodiment of the vehicle, the airbag module includes anelongate inflator arranged in the dashboard and extending across alength of the dashboard. The inflator has multiple inflation portsleading to the airbag. If the airbag includes one or more vents, a ventcontrol mechanism is provided to control the flow of gas through thevent(s). For example, one or more valves may be associated with thevent(s) and a torsional spring used to control opening of the valve(s).Alternatively or additionally, the upper surface of the dashboardincludes one or more vents.

Another embodiment of a steering wheel assembly for a vehicle inaccordance with the invention includes a steering column having firstand second opposite ends, the first end being adapted to be mounted tothe vehicle, a steering wheel mounted at the second end of the steeringcolumn which is pivotable relative to the first end of the steeringwheel, and an airbag mounted at the second end of the steering wheel. Toenable the pivotal movement of the second end relative to the first end,the steering column has a first part defining the first end and a secondpart defining the second end, and possibly a joint pivotally connectingthe first and second parts. An actuating mechanism may be provided topivot the second part about the joint relative to the first part. Thisactuating mechanism could be coupled to a crash sensor and arranged toreceive a signal from the crash sensor indicative of an impending oractual crash and pivot the second part to adjust a position of thesteering wheel.

Another important object of at least one invention disclosed herein isto form a tubular airbag from flat sheets of film or composite material,or by blow molding or a similar process in order to create an airbag foruse to protect occupants in the event of a crash of the vehicle, whichmay be substantially larger than current airbags and which may bedesigned to interact with the occupant regardless of where he/she ispositioned without causing significant injury and thereby to improve theprotection provided by the airbag. One of the materials for the airbagcan be selected from the class of plastic materials known asthermoplastic elastomers which includes, among others, polyurethane,polyester elastomer and metallocene-catalyzed polyolefin. A plasticmaterial is called an elastomer when its elongation prior to failure islarge, sometimes as large as 100%, 200%, 400% or more. The driver airbagversion can use the inelastic properties of a layer of the film materialto cause the airbag to attain the desired shape without requiring theuse of tethers. As a driver side airbag, for example, it can besubstantially elliptical in two orthogonal planes and circular in athird orthogonal plane. If a composite material composed of film and anet, an inelastic film and an elastic film, or film and a fabric, isused to form a hybrid design, the relatively inelastic properties of thefilm are used to create the desired flat elliptical shape, for example,while the net, elastic film or fabric is used to provide other desirablefeatures including tear resistance sometimes known as blunting.

Another important object of at least one invention disclosed herein isto create a plurality of airbags each composed of tubes, compartments orcells made from plastic film which are designed to impact with a vehicleoccupant without causing injury and to hold the occupant in his or herpre-crash position during the crash of the vehicle. The inflation ofsuch airbags is accomplished with an inflator system that providessufficient gas to inflate the airbags without over-inflating them, thusrendering the airbag system self-adjusting to the occupancy state of thecompartment.

The present invention when applied to knee bolsters can take the form ofa cellular knee bolster that preferably is made from plastic film. Itcan protect the knees, femurs and lower torso as well as the feet,ankles, and lower legs of the occupant by creating an inflatablerestraint that deploys in front and around the occupant's knees andlegs, restrains the occupant from all directions and/or inhibits theforward and downward movement by the occupant during a frontal crash. Itprotects the knees by preventing the knees from becoming trapped in orunderneath the dashboard. Further, by transferring energy from the lowertorso of the occupant through the femur and knees to the bolster, thisinvention reduces the severity of injuries to those body parts as well.This invention also reduces the severity of lower torso injuries due toseat belt pressure by stabilizing the lower body and preventing theknees and legs from moving forward, thus allowing the seat belt toremain in its preferred position on the occupant.

This embodiment of the present invention improves egress and extractionof the occupant from a vehicle after a crash because it prevents theoccupant from becoming wedged into or underneath the interior structure.Since this invention is small in size prior to being deployed, it doesnot intrude into or occupy significant space within the occupantcompartment as does a conventional fixed knee bolster. This is a majoradvantage from not only the entry, egress and overall comfortviewpoints, but also from an aesthetic design consideration.

This embodiment of the invention can be installed beneath or as part ofthe lower face of the dashboard. It then deploys downward as a pluralityof independent cells that can be in the form of tubes that can be joinedtogether at their ends with a sheet that then conforms and wraps aroundthe knees and legs of the occupant. Support is achieved since virtuallythe entire volume is filled with small cellular airbags that aresupported by each other and by the vehicle structure.

The gas generator which inflates the unit can be mounted remotely in aconvenient location, such as forward in the dashboard, using a flexibleor combination rigid/flexible gas conduit.

In the event of a crash, a crash sensor signals the gas generator toignite and discharge gas at a high mass flow rate into the gas conduitleading to a manifold and to the bolster. The bolster cells inflateuntil the pressure rises above a design value which then chokes offfurther flow to the cells and individual valves in each of the cellsthen close thereby preventing the gas from exhausting from the cells.Thus, within about 10 to 25 ms after impact (or earlier if ananticipatory sensor is used), the cellular cushion positions itself infront and around the occupant's legs and knees, restrains forward anddownward occupant movement, cushions the occupant from impact, andfunctions as a barrier between the occupant's knees and legs and thevehicle's structure. The bolster expands to meet the occupant and thusthere is no impact of the occupant with the bolster during the crash.The restraining forces on the occupant are transferred to the vehicle'sstructure through this bolster. When the impact has passed and theoccupant is at rest, he or she relaxes the load on the bolster and isvery close to his or her initial position.

Another important difference between this invention and prior art isthat the present invention can be installed without any reactive surfacebehind the invention. Most prior art restraint devices of this typerequire the dashboard to extend low enough to provide a reactive surfacefor either the knees or a conventional airbag. This invention does notrequire this additional surface area protruding from the dashboard sinceit is supported by the filling of the entire volume with airbags whichare effective to transfer the reaction to whatever vehicle structure isavailable, such as the firewall. This invention therefore allows moreleg room for the occupant in its non-inflated condition, increasingoccupant comfort and reducing the possibility that the occupant will betrapped beneath the dashboard during a crash. Since prior art restraintdevices require strong reactive surfaces, the total system (module andsupport structure) can be heavy and/or bulky. The present invention doesnot include nor require a heavy support structure since it employs thealready existing vehicle side structure and/or tunnel.

Fixed bolsters cannot provide optimal protection for both small andlarge occupants because seat positions vary. A small occupant, forexample, sitting in a rearward seat position, as commonly occurs on thepassenger side, will come off the seat prior to contacting a fixedbolster. The occupants can thus be injured by hitting the rigid paddingor structure of the bolster. Since the present invention can be anon-rigid structure that can be designed to meet the occupant whereverhe or she is sitting, no injuries should result from hitting thebolster.

Airbags of the present invention may be inflated to a range of volumesdepending on the particular vehicle installation. The typical airbaginflation completely fills the space between the knees and the footwell. The present invention, therefore, is an important contribution tovehicular crashworthiness and occupant leg and torso protection infrontal impacts and is particularly a substantial improvement ininflatable vehicular knee bolsters.

In order to achieve other objects of the invention, a vehicle isprovided with a knee protection airbag which has a storage position anda deployed position and an inflator which inflates the airbag from thestorage position to the deployed position so that the airbagsubstantially fills a space between the knees of the occupant whenseated on the front seat and an instrument panel in the deployedposition. By filling the space between the knees and the instrumentpanel, injury to the knees, and other body parts, is prevented.

Inflation of the airbag is caused by a determination by a crash sensorsystem of an actual or expected crash involving the vehicle and mayinclude an anticipatory crash sensor which forecasts a crash between thevehicle and another object prior to impact of the vehicle by the otherobject. In this manner, the airbag is inflated prior to the crash.

Various constructions of the airbag are possible. In one construction,the airbag includes at least two pieces of substantially flat inelasticplastic film having peripheral edges, one of which has an inlet port forinflow of inflating fluid, and the pieces of inelastic plastic film areattached together at least at peripheral edges to form a substantiallysealed airbag. The airbag may have interconnected chambers formed byattaching the pieces of inelastic plastic film together. In anotherconstruction, the airbag includes inelastic plastic film, an inlet portfor inflow of inflating fluid and a variable outlet vent which isdesigned to open variably in response to pressure in the airbag. Inanother construction, the airbag includes a single piece of inelasticplastic film having an inlet port for inflow of inflating fluid. In yetanother construction, the airbag includes an outer airbag made of atleast one layer of plastic film and an inner airbag made of at least onelayer of plastic film and arranged to fill an interior volume of theouter airbag when inflated.

In still another embodiment, the airbag includes a first sheet of filmand a member arranged in connection therewith for arresting thepropagation of a tear therein. The member may be (a) a network ofmulti-directional material strips; (b) a second sheet of film havingsubstantially anisotropic tear properties with the direction of tearresistance thereof being different than a direction of tear resistanceof the first sheet of film; and (c) a thermoplastic elastomeric materialarranged at specific locations such that the locations are thicker incomparison to an average thickness of the first sheet of film.

In still another embodiment, the airbag includes a composite airbaghaving at least one layer of inelastic plastic film attached to a layerof a more elastic plastic film, the second layer serving to blunt thepropagation of a tear.

In another embodiment, the airbag includes a plurality of materialsections defining a plurality of interconnected cells, each of which hasa width less than a width of the occupant's knees. Optionally, theairbag includes one-way valves arranged in the material sections betweenthe cells to control flow of inflating fluid between the cells. One ormore of the valves leads to each cells and the valves are arranged toclose once a predetermined pressure prevails in the respective one ofthe cells to prevent fluid outflow from the cell.

In yet another embodiment, a net surrounds the airbag during and afterdeployment of the airbag.

The inflator may include a gas generator for producing pressurized gasto inflate the airbag and an aspiration system which combines gas fromthe passenger compartment of the vehicle with pressurized gas from thegas generator and directs the combined flow of gas into the airbag.

Another knee bolster airbag system for protecting the knees of anoccupant of a vehicle includes an airbag having a plurality of cells, aninflator arranged to inflate the airbag and a housing for storing theairbag, the housing being mounted in the vehicle in a position in whichthe airbag engages lower extremities of the occupant upon inflation.Preferably, the airbag is dimensioned to occupy a space between theoccupant's legs and structural components of an instrument panel of thevehicle when inflated.

Another knee bolster airbag system for a vehicle includes an airbaghaving a plurality of chambers and an inflator arranged to inflate theairbag such that the airbag engages the lower extremities of a vehicleoccupant upon inflation and distribute impact force imposed by the lowerextremities over the chambers. The airbag provides a soft surfaceadapted to engage the lower extremities of an occupant. Optionally, theairbag is arranged such that when inflated, it occupies a space betweenthe occupant's legs and the vehicle instrument panel such that theinstrument panel provides support for the airbag. In one embodiment, theinflator is arranged to direct gas directly into only a portion of thechambers and the airbag includes a plurality of one-way valves arrangedbetween adjacent chambers to enable flow of gas from the inflator to allof the chambers.

Another vehicle equipped with a knee bolster airbag system in accordancewith the invention includes a compartmentalized airbag knee bolsterdevice mounted to the instrument panel and including an inflator forproviding pressurized gas upon actuation thereof and a compartmentalizedairbag having a plurality of compartments in communication with theinflator. The compartmentalized airbag knee bolster device is mounted tothe instrument panel such that the compartmentalized airbagsubstantially occupies a space between the instrument panel and theknees or lower extremities of an occupant situated in front of theinstrument panel when inflated. The compartmentalized airbag may includea plurality of material sections defining a plurality of compartmentsand one-way valves arranged in the material sections between thecompartments to control flow of inflating fluid between thecompartments. Each compartment can have a width approximately equal toor less than the width of a knee of an occupant of the motor vehicle.

An inflatable tubular bolster for a vehicle in accordance with theinvention includes an inflatable airbag having a plurality of cells, agas generator fluidly connected to the airbag via a gas conduit and acrash sensor connected to the gas generator for detecting an impactinvolving the vehicle. When an impact is detected by the crash sensor,the gas generator causes the cells to be inflated and the airbag deploysfrom a stowed position downward and rearward into a position below aninstrument panel of the vehicle such that it restrains forward anddownward movement of an occupant situated in front of the instrumentpanel. The airbag may be arranged to deploy in front of an occupant'sknees and thereby inhibits forward and downward movement of theoccupant.

A system for protecting occupants of a vehicle during a crash involvingthe vehicle in accordance with the invention includes a plurality ofinflators for generating pressurized gas, a crash sensor system forcontrolling the inflators to begin generating pressurized gas based on acrash involving the vehicle, a plurality of primary airbags eachdirectly connected to a respective inflator and receiving pressurizedgas directly from the respective inflator and at least one secondaryairbag in flow communication with each primary airbag such thatinflation of the primary airbag by the respective inflator causesinflation of the secondary airbag(s). This resembles a chain reaction ofinflating airbags which progresses from an airbag closest to the vehiclestructure inward until contact is made by a secondary airbag with theoccupant. Thus, when a plurality of secondary airbags are present anddistanced sequentially from the primary airbag, gas from the primaryairbag passes into a first one of the secondary airbags and from thefirst secondary airbag to a second one of the secondary airbags and soon. The secondary airbags may include a one-way valve which enables flowof gas from each secondary airbag to an adjoining downstream secondaryairbag. Each primary airbag may also include a one-way valve whichenable flow of gas from the primary airbag to an adjoining secondaryairbag.

In one particular embodiment, the crash system includes an anticipatorycrash sensor arranged to determine whether a crash involving the vehicleis about to occur and to direct the inflators to generate gas prior tothe crash such that the primary airbags and the at least one secondaryairbags are inflated prior to the crash. In this manner, the entireunoccupied interior space of the passenger compartment can be filed withairbags to cushion any occupants in a crash.

Each inflator may include a gas generator for producing pressurized gasto inflate a respective primary airbags and an aspiration system forcombining gas from the passenger compartment of the vehicle withpressurized gas from the gas generator and directing the combined flowof gas into the respective primary airbag.

It is an object of the present invention to provide a new and improveddischarge valve for an airbag.

It is another object of the present invention to provide a new andimproved discharge valve for controlling flow of gas from an airbag.

It is yet another object of the present invention to provide a new andimproved airbag including or incorporating a discharge valve whichprovides benefits over conventional airbag discharge valves.

It is still another object of the present invention to provide new andimproved control systems for controlling inflation and/or deflation ofan airbag using discharge valves and more particularly, to controlsystems which tailor the inflation and/or deflation to the properties ofthe occupant to be protected by the deploying airbag, e.g., theposition, identification, type, morphology of the occupant.

It is another object of the invention to provide and new and improvedvalve which enables dynamic control of the flow of gas out of an airbagwhich is particularly useful in smart airbags.

In order to achieve at least one of the above objects, one embodiment ofa discharge valve for an airbag in accordance with the inventioncomprises a fixed plate adapted to be arranged in connection with orassociated with the airbag and having a pattern of openings and amovable plate arranged over the fixed plate and having a pattern ofopenings substantially identical to the pattern of openings of the fixedplate. The movable plate is movable relative to the fixed plate to varythe correspondence between the openings on the movable plate and theopenings in the fixed plate to thereby vary valve openings defined bythe fixed plate and the movable plate. Variation in the valve openingsresults in control and/or regulation of the outflow of gas from theairbag through the discharge valve.

Instead of a movable plate and a fixed plate, a pair of concentriccylinders could be used having substantially identical patterns ofopenings. One cylinder would be rotated or stroked relative to the fixedcylinder to modulate the openings. The fixed cylinder could be theinternal cylinder or the external cylinder.

In another embodiment, instead of plates or cylinders, a pair of conescould be used having substantially identical patterns of openings. Onecone would be rotated or stroked up and down relative to the fixed coneto modulate the openings. The fixed cone could be the inner cone or theouter cone.

Thus, in general, any two members may be used in the invention, onemovable relative to the other. The member may be a plate, cylinder orcone, or possibly have other forms.

Other possible features of this embodiment includes a spring connectedto the movable member for allowing movement of the movable member and amovement mechanism for moving the movable member relative to the fixedmember. The movement mechanism may comprise a piezo-electric bi-morphcrystal arrangement arranged in connection with the movable member formodulating the movable member to thereby control the valve openings. Thepiezo-electric crystal arrangement can be driven by a drive signal andassociated electronics. When present, the spring is connected to anopposite side of the movable member from the piezo-electric crystalarrangement. The movement mechanism can also comprise an inductivesolenoid motion or motor arrangement with a cam offset.

Another embodiment of a discharge valve for an airbag comprises adiaphragm composed of foil and including concentric grooves and amechanism for weakening at least one of the grooves whereby thediaphragm is severable along the groove(s) upon exertion of pressure.The foil may be metallic or another type of material which is can bemelted upon application of an electric current. The mechanism to weakenthe grooves may therefore be the creation of one or more electriccircuit, such as a capacitive discharge circuit. A high impedance isformed at the grooves by reducing the cross sectional area. This createsa high resistance at the groove thus causing thermal melting of thegroove and/or grooves. A logic circuit may be provided to determine towhich circuit a signal is fed to cause weakening of the associatedgroove(s). The logic circuit can be designed to consider properties ofan occupant to be protected by the airbag.

Another embodiment of a discharge valve for an airbag in accordance withthe invention comprises a flexible diaphragm adapted to be fixed to theairbag and having apertures therein. The diaphragm is made of elasticmaterial such as from one or more elastomers. The diaphragm is adaptedto be fixed by its edges to the airbag and can be circular. When theelastomer expands, the apertures in the elastomer also expand therebyincreasing the discharge rate.

Still another embodiment of a discharge valve for an airbag inaccordance with the invention comprises a fixed disk adapted to bearranged in connection with or associated with the airbag and includingapertures, a movable disk mounted over the fixed disk and includingsolid sections and open sections, and an arm connected to the movabledisk. The arm is movable to vary correspondence between the apertures inthe movable disk and the apertures in the fixed disk to thereby varyvalve openings defined by the fixed disk and the movable disk.

Other features of this embodiment include a mounting pin for rotatablymounting the movable disk to the fixed disk and a movement mechanism formoving the arm. The movement mechanism may comprise a solenoid, bi-morphpiezo-electric element, ferromagnetic arrangement or drive or athermal-based arrangement such as a phase change metal.

Yet another embodiment of a discharge valve for an airbag in accordancewith the invention comprises a valve seat adapted to be arranged inconnection with the airbag, a valve member engaging with the valve seatto selectively close at least one passage defined between the valve seatand the valve member, and a valve spring arranged to provide a biasingforce to press the valve member against the valve seat to close thepassage(s).

In another embodiment of a discharge valve for an airbag in accordancewith the invention, the discharge valve comprises a substrate having atleast three spiral cuts arranged to form cantilevered arms capable ofdeflecting under pressure. The spiral cuts extend from a peripheral edgeof the substrate to an interior region of the substrate.

Another substrate of a discharge valve may comprise cuts definingcantilevered arms capable of deflecting under pressure. The cuts definecantilevered arms, and possibly a central region with the cantileveredarms connecting the central region to a peripheral edge of thesubstrate. In the latter case, the central region is deflected from aplane of remaining portions of the substrate upon deflection underpressure. The cantilevered arms could form a very non-linear forceprofile that could mechanically modulate the discharge rate.

4 Systems

Other objects of this invention and of the broader invention of smartairbags include:

1) The use of pattern recognition techniques such as a neural network,or neural-network-derived algorithm, to analyze the digitizedaccelerometer data (also referred to as acceleration data herein)created during a crash and, in some cases, occupant size, position,seatbelt use, weight and velocity data, and, in other cases, data froman anticipatory crash sensor, to determine not only if and when apassive restraint such as an airbag should be deployed but also tocontrol the flow of gas into or out of the airbag.

2) To provide a single point sensor including an accelerometer thatmakes maximum use of the information in the acceleration data todetermine not only whether an airbag should be deployed but also therate of deployment as required for Phase 3 Smart Airbags.

3) To provide a single point sensor including an accelerometer whichmakes maximum use of the information in the acceleration data todetermine not only whether an airbag should be deployed but the totalamount of gas which should be used to inflate the airbag as required forPhase 3 Smart Airbags.

4) To provide a single point sensor including an accelerometer whichmakes maximum use of the information in the acceleration data todetermine the gas flow control parameter value for use by a gas controlmodule to control the flow of gas into or out of an airbag as requiredfor Phase 3 Smart Airbags.

5) To provide a single computer system which can perform severaldifferent pattern recognition functions within an automobile or othervehicle including, for example, crash sensing and severity prediction,anticipatory sensing, identification of an occupant located within thevehicle passenger compartment and determination of the position andvelocity of the occupant.

6) To provide a crash sensor and crash severity prediction algorithmwhich is derived by training using a set of data derived from stagedautomobile crashes and non-crash events as well as other analyticallyderived data, as required for Phase 3 Smart Airbags.

7) To provide a crash sensor and/or crash severity prediction algorithmbased on pattern recognition techniques.

8) To provide a crash sensor and crash severity prediction algorithmwhich uses other data in addition to acceleration data derived from thecrash wherein this data is combined with acceleration data and, usingpattern recognition techniques, the need for deployment and the rate ofdeployment of a passive restraint is determined.

9) To provide a crash sensor and crash severity prediction algorithmusing data from an anticipatory sensor and an occupant position andvelocity sensing system to optimize the deployment of a passiverestraint system taking into account the crash severity and occupantdynamics to minimize injuries to the occupant as required for Phase 4Smart Airbags.

10) To provide an electronic module which combines the functions ofcrash sensing and crash severity prediction, occupant position andvelocity sensing, anticipatory sensing (as required for Phase 4 SmartAirbags) and airbag system diagnostics.

11) To provide a Phase 1, Phase 2, Phase 3 or Phase 4 Smart Airbagsystem that uses a neural computer.

12) To provide a smart airbag system that optimizes the deployment of anoccupant protection apparatus in a motor vehicle, such as an airbag, toprotect an occupant of the vehicle in a crash by controlling the flow ofinflator gas into or out of the airbag.

13) To provide a self-contained side impact occupant protection airbagsystem incorporating the advantages of a movable mass sensor resultingin a low cost, compact airbag system.

14) To provide a more compact self-contained side impact airbag systemby providing for the exhausting of the airbag gas into the vehicle dooror side, therefore permitting the use of higher temperature gas andpropellants which would otherwise not be viable due to their toxicproducts.

15) To provide a highly reliable side impact occupant protectionelectronic self-contained airbag system.

16) To provide an electronic, electromechanical or mechanical sensor foruse with either a self-contained airbag system or conventional airbagsystem wherein the sensor system senses the acceleration of the vehiclemember on which it is mounted and where in the sensed acceleration isthe crush zone acceleration and is used to control the deployment of theside airbag.

17) To provide a universal single point crash sensor and diagnosticmodule which can be used on most automobiles without any modificationrequired specific to each automobile.

18) To provide a single computer system which can perform severaldifferent pattern recognition functions within an automobile including,for example, crash sensing, identification of an object located withinthe vehicle passenger compartment, and the categorization of objectsexterior to the vehicle.

19) To provide a sensor and diagnostic module comprising a crash sensoralgorithm which is derived by training using a set of data derived fromstaged automobile crashes and non-crash events as well as otheranalytically derived data.

20) To provide a sensor and diagnostic module comprising a crash sensorbased on pattern recognition techniques.

21) To provide a sensor and diagnostic module comprising a crash sensorwhich uses other data in addition to acceleration data derived from thecrash wherein this data is combined with acceleration data and, usingpattern recognition techniques, the need for deployment of a passiverestraint is determined.

22) To provide a sensor and diagnostic module comprising a crash sensorwhich can be used for sensing frontal, side, and rear impacts.

23) To provide a sensor and diagnostic module comprising a crash sensorwhich automatically retains the crash acceleration data from a period oftime prior to the airbag deployment for later analysis.

24) To provide a sensor and diagnostic module comprising a crash sensorthat uses a neural computer.

To achieve one or more of these objects, a sensor and diagnostic modulein accordance with the invention comprises a sensor system forinitiating deployment of an occupant protection apparatus in a motorvehicle, such as an airbag, to protect an occupant of the vehicle in acrash. The system includes a sensor mounted to the vehicle for sensingaccelerations of the vehicle and producing an analog signalrepresentative thereof; an electronic converter for receiving the analogsignal from the sensor and for converting the analog signal into adigital signal, a processor which receives the digital signal, adiagnostic system which determines that the sensor and its variouscomponents are functioning correctly and a storage device for storingthe state of the system at the time of a crash plus, in some cases, atime history of the data, including digitized accelerometer data, usedby the system to determine whether or not the passive restraint shouldbe deployed. The processor includes a pattern recognition system andproduces a deployment signal when the pattern recognition systemdetermines that the digital signal contains a pattern characteristic ofa vehicle crash requiring occupant protection.

One embodiment of the method for initiating deployment of an occupantprotection apparatus in accordance with the invention comprises sensingaccelerations of the vehicle and producing an analog signalrepresentative thereof, converting the analog signal into a digitalsignal, determining if the digital signal contains a patterncharacteristic of a vehicle crash requiring occupant protection by meansof a pattern recognition system, or a single neural computer comprisinga pattern recognition system, producing a deployment signal upon adetermination by the pattern recognition system that the digital signalcontains the pattern characteristic of a vehicle crash requiringoccupant protection, and initiating deployment of the occupantprotection apparatus in response to the deployment signal. The patternrecognition system may comprise a single trained neural network suchthat the deployment signal is produced solely by the utilization of thesingle trained neural network. The digital signal may be derived fromthe integral of the analog signal. One or more sensors may be arrangedto sense the accelerations of the vehicle and which are mounted in aposition on the vehicle so as to sense frontal impacts and/or rearimpacts. Additionally, data from other sensors such as gyroscopes orangular rate sensors, velocity and position sensors, may be used whenavailable by the trained neural network. In certain advantageousembodiments, the method detects when the occupant to be protected by thedeployable occupant protection apparatus is out-of-position andsuppresses deployment of the occupant protection apparatus if theoccupant is detected as being out-of-position. Similarly, the presenceof a rear-facing child seat positioned on a passenger seat, i.e., andwhich would be affected by the occupant protection apparatus, can bedetected and deployment of the occupant protection apparatus suppressedif a rear-facing child seat is detected.

Accelerations of the vehicle may be measured in two or more directions.In the embodiment wherein a neural computer is used, data from ananticipatory sensor and/or a collision avoidance sensor may be inputinto the single neural computer for consideration during the patternrecognition analysis.

At least one invention herein is primarily concerned with a novelself-contained airbag system for protecting occupants in side impacts.It is also concerned with the sensors used either with self-containedmodules or apart from the airbag module. This is accomplished by usingthe sensors described in U.S. Pat. No. 5,231,253, along with otherimprovements described in detail below. This invention is secondarilyconcerned with applying some of the features of the novel side impactsystem to solving some of the problems of prior art mechanical airbagsystems discussed above.

The sensitivity to cross axis accelerations of current all mechanicalairbag systems, for example, is solved in the present invention, asdiscussed in U.S. Pat. No. 5,233,141 through the substitution of ahinged sensing element for the ball sensing mass in the Thuen patent.

The problems resulting from the hole in the inflator wall when apercussion primer is used as in Breed, U.S. Pat. No. 4,711,466, aresolved in inventions disclosed herein through the placement of sensitivepyrotechnic material in a cavity adjacent to the outside wall of theinflator and then using shock from a stab primer to initiate thepyrotechnic material and thus the inflator. An alternate solution, asdiscussed below, is to make the size of the hole created in the inflatorby the action of the stab primer small so that the total quantity of gaswhich escapes into the sensor is small compared with the quantity of gasused to inflate the airbag.

Finally, in some self-contained airbag systems disclosed herein,provision is made to exhaust the gas outside of the passengercompartment, into the vehicle doors, or other side areas of the vehicle.This permits the use of higher gas temperatures and alternate propellantformulations, such as nitro-cellulose, which produce toxic combustionproducts. Both of these changes reduce the size, weight and cost of thesystem.

Briefly, the self-contained airbag system includes a sensor having amovable sensing mass, a mechanism to sense the position of the sensingmass to determine if the airbag should be deployed, a sealed housing, agas generator for producing the gas to inflate the airbag, an airbag,and mounting hardware.

The sensors used here are either electronic, electro-mechanical ormechanical but all have a movable mass where the motion of the mass issensed either electronically or mechanically.

Further objects and advantages of some of the inventions herein are:

1) To provide a self-contained side impact occupant protection airbagsystem incorporating the advantages of a movable mass sensor resultingin a low cost, compact airbag system.

2) To provide a frontal impact all mechanical airbag systemincorporating a hinged sensing mass to eliminate the effects ofcross-axis accelerations on the operation of the sensor.

3) To provide a method of minimizing the leakage of the inflator gasesout of the inflator portion of a self-contained airbag system into thesensor portion and the associated problems.

4) To provide a side impact airbag system which utilizes the crush ofthe vehicle side to arm the sensor and motion of a sensing mass toinitiate deployment.

5) To provide a method of hermetically sealing a self-contained airbagsystem while permitting an external force to be used to arm the system.

6) To provide a more compact self-contained side impact airbag system byproviding for the exhausting of the airbag gas into the vehicle door orside, therefore permitting the use of higher temperature gas andpropellants which would otherwise not be viable due to their toxicproducts.

7) To provide an all-mechanical airbag system utilizing a cantileveredfiring pin spring which also provides the biasing force on the sensingmass thereby providing a simplified design.

8) To provide an all-mechanical airbag system with a thin sensor mountedoutside of the inflator housing but in line with it to reduce the sizeof the system and permit the use of conventional inflator designs.

9) To provide a highly reliable side impact occupant protectionelectro-mechanical self-contained airbag system.

10) To provide a highly reliable side impact occupant protectionelectronic self-contained airbag system.

11) To provide a method of obtaining the power for an electricalself-contained airbag system from other components within the doorthereby minimizing the requirement for separate wiring for the airbagsystem.

12) To provide a power supply within the self-contained module and asimplified diagnostic system for an electrical self-contained airbagsystem.

13) To provide a self-contained airbag system design that permits thearming of the sensor after it has been mounted onto the vehicle butbefore the inflator is mounted to provide greater safety againstunwanted deployments.

14) To provide an electronic, electromechanical or mechanical sensor foruse with either a self-contained airbag system or conventional airbagsystem wherein the sensor system senses the acceleration of the vehiclemember on which it is mounted and where in the sensed acceleration isthe crush zone acceleration and is used to control the deployment of theside airbag.

Other objects and advantages will become apparent from the discussionbelow.

In order to achieve at least some of the above objects above, a sideairbag system in accordance with one embodiment of the vehicle includesan airbag arranged to deploy in the event of an impact into a side ofthe vehicle, a side impact crash sensor arranged to sense an impact intoa side of the vehicle, and an inflator for inflating the airbag. Thecrash sensor is an electrical sensor which includes a movable sensingmass which moves when the side of the vehicle is impacted and a signalgenerating mechanism for generating a time-varying signal representativeof movement of the sensing mass, analyzing the signal representative ofthe movement of the sensing mass and generating a deployment signalbased thereon. The inflator is coupled to the crash sensor and receivesthe deployment signal therefrom and inflates the airbag upon receipt ofthe deployment signal.

The signal generating mechanism may comprise a micro-processor whichprocesses signals representative of the continuous movement of thesensing mass. The movement of the sensing mass may be recorded over timewhile the micro-processor includes an algorithm arranged to determinewhether the movement of the sensing mass results in a calculated valuewhich is in excess of a threshold value in order to generate thedeployment signal.

The electrical sensor may also comprise an accelerometer. The signalgenerating mechanism may comprise a strain gage or a piezo-electricelement. The airbag may be arranged around the inflator and the crashsensor may be arranged proximate the inflator.

Some vehicles in accordance with the invention have a front, a rear,left and right sides and at least one door arranged on each of the leftand right sides, an airbag arranged to deploy along the left or rightside of the vehicle in the event of an impact into the left or rightside of the vehicle, a side impact crash sensor arranged to sense animpact into the left or right side of the vehicle, and an inflator forinflating the airbag. The crash sensor, as well as the other componentsof the vehicle, may be as described above.

A method for protecting an occupant in a vehicle comprises arranging anairbag in the vehicle in a position to protect the occupant in the eventof an impact into a side of the vehicle, sensing an impact into a sideof the vehicle by continuously monitoring movement of a sensing mass togenerate a time-varying signal representative of movement of the sensingmass and analyzing the signal representative of the movement of thesensing mass to generate a deployment signal based thereon, anddirecting the deployment signal to an inflator to cause the inflator toinflate the airbag. A micro-processor processes the signalrepresentative of the movement of the sensing mass and optionallyincludes an algorithm arranged to determine whether the motion over timeof the sensing mass results in a calculated value which is in excess ofa threshold value in order to generate the deployment signal.

Accordingly, it is an object of at least one present invention toprovide a new and improved airbag module in which the disadvantages andproblems in the prior art airbag module designs are substantiallyeliminated.

It is a particular object of this invention to provide a new andimproved airbag module in which the propellant is utilized moreefficiently than in prior art constructions, i.e., more of the energygenerated by the burning propellant is used to inflate the airbag withless waste of generated energy.

It is yet another object of at least one present invention to provide anew and improved airbag module in which the propellant is utilized moreefficiently than in prior art constructions so that a smaller amount ofpropellant can be used thereby enabling a wider variety of propellants,which may generate toxic gases, to be used since only small quantitiesof such toxic gases will be generated.

It is still another object of the present invention to provide a new andimproved airbag module for a side curtain airbag, e.g., one in which oneor more airbags deploy along a side of the vehicle.

Other objects and advantages of the present invention will becomeapparent from the following description of the preferred embodimentstaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of embodiments of the inventionand are not meant to limit the scope of the invention as encompassed bythe claims.

FIG. 1 is a view of the front of the passenger compartment of a motorvehicle, with portions cut away and removed, having dual airbags and asingle point crash sensor and crash severity forecaster including anaccelerometer and using a pattern recognition technique.

FIG. 1A is an enlarged view of the sensor and diagnostic module shown inFIG. 1.

FIG. 2 is a diagram of a neural network used for a crash sensor andcrash severity forecaster designed based on the teachings of inventionand having more than one output node.

FIG. 3 contains the results of a neural network algorithm on a crashmatrix created using the techniques of velocity and crash scaling.

FIG. 4 contains the results of a standard single point crash sensor on acrash matrix created using the techniques of velocity and crash scaling.

FIG. 5 is a perspective view of a preferred embodiment of the sensor ofthis invention for use in frontal impacts shown removed from thevehicle.

FIG. 6 is a perspective view taken along line 6-6 of the sensor shown inFIG. 5 with the interior parts pulled apart to illustrate the interiorstructure.

FIG. 7 is a frontal view of another preferred embodiment of the sensorof shown mounted on a vehicle to sense frontal impacts with portions ofthe vehicle removed to permit viewing of the sensor.

FIG. 7A is a view of a vertical segment of the sensor shown in FIG. 7taken along line 7A-7A in a condition before being impacted by thevehicle bumper during a crash.

FIG. 7B is the same view of the sensor shown in FIG. 7A after beingimpacted by the vehicle bumper during a crash.

FIG. 8 is a partial view of an alternate configuration of a verticalportion of the sensor of FIG. 7 showing it displaced rearward to reduceits sensitivity to impacts above the bumper.

FIG. 9 is a view of a vehicle taken from the side, with certain portionsremoved, which is about to impact a low pole which misses the bumper,illustrating the ability of the sensor to respond to this type of crash.

FIG. 10 is a side view of another preferred embodiment of the sensor inaccordance with the invention shown mounted on a vehicle in a positionto sense side impacts, with portions of the vehicle removed to permitviewing of the sensor.

FIG. 11 is a rear view of another preferred embodiment of the sensor inaccordance with the invention shown mounted on a vehicle in a positionto sense rear impacts with portions of the vehicle removed to permitviewing of the sensor.

FIG. 12 is a cutaway view of the header/connector assembly of FIG. 5taken along line 12-12 illustrating the construction details and inparticular the method of sealing the sensor.

FIG. 13 is a partial cutaway view of a portion of the sensorillustrating a bend in the sensor.

FIG. 14 is a cutaway of the sensor end showing the welded seal.

FIG. 15 is a view of the sensor of FIG. 5 taken along the line 15-15with part of the tube and rod cut away illustrating the positioning ofspacers within the sensor and their use to change the sensitivity of thesensor to deformation.

FIG. 16 is a view of the sensor of FIG. 5 with portions of the tube androd cut away illustrating the use of a grease to fill the cavity betweenthe rod and tube to minimize the effects of vibration and to protect thesurfaces of the conductors from corrosion.

FIG. 17 is a side view of another preferred embodiment of a sensor inaccordance with the invention shown mounted on a vehicle in a positionto sense both frontal and side impacts, with portions of the vehicleremoved to permit viewing of the sensor.

FIG. 18 is a perspective view of an automobile, as viewed partially fromabove, of a side impact anticipatory sensor system using the samecomputer as the single point crash sensor and also showing inputs from afront mounted crush zone sensor, an engine speed sensor, and an antilockbraking system sensor.

FIG. 19 is a frontal view of an automobile showing the location of anelectromagnetic wave crash anticipatory or avoidance sensor which usesthe same pattern recognition computer system as the crash sensor.

FIG. 20 is a circuit schematic showing a side mounted velocity sensorused with a non-crush zone mounted sensor.

FIG. 21 is a circuit schematic showing a forward mounted sensor used asan input to an electronic sensor.

FIG. 21A is a circuit schematic showing a forward mounted ball-in-tubesensor used as an input to a crash sensor mounted outside of the crushzone.

FIG. 21B is a circuit schematic showing a forward mounted electronicsensor used as an input to a crash sensor mounted outside of the crushzone.

FIG. 21C is a schematic of an electronic crash sensor arrangementincluding a crush-zone mounted crash sensor and a non-crush-zone mountedcrash sensor.

FIG. 21D is a flow chart showing the manner in which an occupantrestraint device may be deployed using the crash sensor arrangement ofFIG. 21C.

FIG. 22 is a perspective view of a side impact airbag systemillustrating the placement of the airbag vents in the door panel and theexhausting of the inflator gases into the vehicle door and also showingthe use of a pusher plate to adjust for the mismatch between the pointof impact of an intruding vehicle and the sensor of a self-containedside impact airbag system.

FIG. 23 is a cross section view of a self-contained side impact airbagsystem using an electronic sensor.

FIG. 24 is a schematic of the electric circuit of an electro-mechanicalor electronic self-contained side impact airbag system.

FIG. 25 is a side view of a vehicle showing the preferred mounting oftwo self-contained airbag modules into the side of a coupe vehicle, oneinside of the door for the driver and the other between the inner andouter side panels for the rear seat passenger.

FIG. 26 is a perspective view of a vehicle with the vehicle shown inphantom illustrating one preferred location of the occupant transducersplaced according to the methods taught in U.S. patent application Ser.No. 08/798,029.

FIG. 26A is a view of the passenger compartment of a motor vehicle, withportions cut away and removed, illustrating an occupant out-of-positionsensor and a rear facing child seat detector, both located on theA-pillar and both using the same computer as the pattern recognitionbased crash sensor.

FIG. 27 is a perspective view of a vehicle seat and headrest containingultrasonic head location sensors consisting of one transmitter and onereceiver.

FIG. 28 is a schematic diagram showing a Phase 4 Smart Airbag System.

FIG. 29 is a schematic illustration of a generalized component withseveral signals being emitted and transmitted along a variety of paths,sensed by a variety of sensors and analyzed by the diagnostic module inaccordance with the invention and for use in a method in accordance withthe invention.

FIG. 30 is a schematic of a vehicle with several components and severalsensors and a total vehicle diagnostic system in accordance with theinvention utilizing a diagnostic module in accordance with the inventionand which may be used in a method in accordance with the invention.

FIG. 31 is a flow diagram of information flowing from various sensorsonto the vehicle data bus and thereby into the diagnostic module inaccordance with the invention with outputs to a display for notifyingthe driver, and to the vehicle cellular phone for notifying anotherperson, of a potential component failure.

FIG. 32 is a flow chart of the methods for automatically monitoring avehicular component in accordance with the invention.

FIG. 33 is a schematic illustration of the components used in themethods for automatically monitoring a vehicular component.

FIG. 34 is a schematic of a vehicle with several accelerometers and/orgyroscopes at preferred locations in the vehicle.

FIG. 35 is a block diagram of an inertial measurement unit calibratedwith a GPS and/or DGPS system using a Kalman filter.

FIG. 36 is a block diagram illustrating a method of obtaining a sensorand prediction algorithm using a neural network.

FIG. 37 is a perspective view with certain parts removed of an allmechanical self-contained airbag system for mounting on the side of avehicle to protect occupants in side impacts.

FIG. 38 is a cross sectional view of the apparatus of FIG. 37 takenalong line 38-38.

FIG. 39 is an enlarged fragmentary view of the sensing mass and attachedlever arm extending from the D-shaft prior to rotation of the sensingmass incident to a crash as adapted to the all mechanical system of U.S.Pat. No. 4,580,810.

FIG. 40 is a similar view as FIG. 39 showing the sensing mass rotated asa result of a crash.

FIG. 41 is a view of the apparatus shown in FIG. 40 taken along line41-41 and rotated 90 degrees to the right.

FIG. 42 is a cross-sectional view of a sensor for use in an allmechanical system where the sensor is mounted outside of the inflatorhousing, shown in an unarmed or safe position prior to assembly with aninflator.

FIG. 43 is a cross-sectional view of the sensor of FIG. 42 shown mountedon an inflator, shown in a fragmentary view, after it has triggered inresponse to a vehicle crash.

FIG. 44 is a cross-sectional view of a through bulkhead initiationsystem adapted to a mechanical self-contained airbag system.

FIG. 45 is a perspective view of a mechanical self-contained airbagsystem using a crush sensing arming system, shown in the state before acrash occurs.

FIG. 45A is a blowup with certain parts removed showing a portion of thesensor shown in FIG. 45 in the unarmed position.

FIG. 46 is a cross-sectional view of the apparatus of FIG. 45 takenalong line 46-46 showing the crush sensing arming system after it hasbeen activated by vehicle crush but before the sensing mass of thediscriminating sensor has begun to move.

FIG. 46A is a blowup with certain parts removed showing a portion of thesensor shown in FIG. 46 in the armed position.

FIG. 47 is a cross-sectional view of the apparatus of FIG. 46, alsotaken along line 46-46, showing the crush sensing arming system after ithas been activated by vehicle crush and showing the sensing mass of thediscriminating sensor after it has moved and released the firing pin,triggering the inflation of the airbag.

FIG. 47A is a blowup with certain parts removed showing portion of thesensor shown in FIG. 47 in the fired position.

FIG. 48 is a perspective view of a side impact airbag systemillustrating the placement of the airbag vents in the door panel and theexhausting of the inflator gases into the vehicle door and also showingthe use of a pusher plate to adjust for the mismatch between the pointof impact of an intruding vehicle and the sensor of a self-containedside impact airbag system.

FIG. 49 is a cross-sectional view of a self-contained side impact airbagsystem using an electro-mechanical sensor.

FIG. 50 is a cross-sectional view of a self-contained side impact airbagsystem using an electronic sensor.

FIG. 51 is a schematic of the electric circuit of an electro-mechanicalor electronic self-contained side impact airbag system.

FIG. 52 is a perspective view, with certain parts removed, of apreferred implementation of the airbag module in accordance with theinvention shown mounted on a ceiling of a vehicle passenger compartmentfor deployment to protect rear seat occupants.

FIG. 53A is a cross-sectional view of the airbag module of FIG. 52 priorto deployment of the airbag.

FIG. 53B is a view of the apparatus of FIG. 53A after the initial stageof deployment where the airbag module has been displaced from themounting surface to open aspirating ports.

FIG. 53C is a cross-sectional view similar to FIG. 53A with the airbagfully deployed taken along lines 53C-53C of FIG. 52.

FIG. 53D is a cross-sectional view similar to FIG. 53C after the airbaghas deployed showing the substantial closure of the aspirating ports.

FIG. 53E is an enlarged view of the high pressure gas generator nozzletaken within circle 53E of FIG. 53A.

FIG. 53F is a perspective view of the apparatus of FIG. 53A, with theairbag and other parts cut away and removed.

FIG. 53G is a cross-sectional view of the apparatus of FIG. 53A withparts cut away and removed illustrating an alternate configuration ofthe invention wherein a slow burning propellant in the form of a thinflat sheet is used.

FIG. 53H is a perspective view of the apparatus as shown in FIG. 53Fwherein a separate inflator is used in place of the propellant in thetube of FIG. 53A and the tube is used here as a method of dispensing theoutput from the inflator to the aspirating nozzle design of thisinvention.

FIG. 53I is a longitudinal cross-sectional view of the inflator moduleshown in FIG. 53A.

FIG. 54A is a cross-sectional view of an alternate embodiment of theairbag module in accordance with the invention where sufficient space isavailable for the aspirating ports without requiring movement of themodule toward the occupant.

FIG. 54B is a cross-sectional view of the embodiment of FIG. 54A withthe airbag deployed.

FIG. 55 is a perspective view of a preferred embodiment of the airbagmodule in accordance with the invention used for knee protection shownin the deployed condition.

FIG. 56 is a view of another preferred embodiment of the invention shownmounted in a manner to provide head protection for a front and a rearseat occupant in side impact collisions and to provide protectionagainst impacts to the roof support pillars in angular frontal impacts.

FIG. 57 illustrates still another preferred embodiment of the inventionused to provide protection for all front seat occupants in a vehiclewhich incorporates servo power steering.

FIG. 58 is a view as in FIG. 57 showing the flow of the inflator gasesinto the passenger compartment when occupants begin loading the airbag.

FIG. 59 shows the application of a preferred implementation of theinvention for mounting on the rear of front seats to provide protectionfor rear seat occupants.

FIG. 60 is a perspective view of a typical module cover design as usedwith the embodiment of FIGS. 53A-53I.

FIG. 61 is a perspective view with portions removed of a vehicle havingseveral deployed airbags and a broken rear window.

FIG. 62A is a fragmented partially schematic cross-sectional view of apyrotechnic window breaking mechanism used in accordance with thepresent invention.

FIG. 62B is a fragmented partially schematic cross-sectional view of anelectromechanical window breaking mechanism used in accordance with thepresent invention.

FIG. 62C is a fragmented cross-sectional view of a window releasemechanism in accordance with the present invention which permits thewindow to be ejected from the vehicle if the pressure in the vehicleexceeds a design value.

FIG. 63 is a fragmented view of a vehicle with the side removed with twoinflated airbags showing the airbag gases being exhausted into theceiling of the vehicle.

FIG. 64 is a perspective view of two knee restraint airbags of a sizesufficient to support the driver's knees.

FIG. 65 is a cross-sectional view of an airbag module showing an airbagand inflator with the inflator sectioned to show the propellant,initiator and squib assembly, and with the sensor and diagnosticcircuitry shown schematically.

FIG. 65A is a detailed sectional view of circle 65A of FIG. 65 showingthe inflator squib incorporating a pyrotechnic delay element.

FIG. 65B is a detailed sectional view of an alternate mechanicaldeployment delay mechanism using the electrical squib to release afiring pin which is propelled into a stab primer by a spring.

FIG. 66 is a perspective view of a ceiling mounted airbag system havingexit ports at the ceiling level for gas to flow out of the airbag, ablow-out panel located low in the passenger compartment and a fanexhaust system also located low in the passenger compartment.

FIG. 66A is an enlargement of the blow-out panel of FIG. 66.

FIG. 66B is an enlargement of the exhaust fan of FIG. 66.

FIG. 67 is a perspective view of the combination of an occupant positionsensor, diagnostic electronics and power supply and airbag moduledesigned to prevent the deployment of the airbag if the seat isunoccupied.

FIG. 68 is another implementation of the invention incorporating theelectronic components into and adjacent the airbag module.

FIGS. 69A, 69B, 69C and 69D are different views of an automotiveconnector for use with a coaxial electrical bus for a motor vehicleillustrating the teachings of this invention.

FIG. 70 is a schematic of a vehicle with several accelerometers and/orgyroscopes at preferred locations in the vehicle.

FIG. 71 is a perspective view with portions cut away and removed of afilm airbag wherein the film is comprised of at least two layers ofmaterial which have been joined together by a process such asco-extrusion or successive casting or coating.

FIG. 71A is an enlarged view of the inner film airbag layer and outerfilm airbag layer taken within circle 71A of FIG. 71.

FIG. 71B is an enlarged view of the material of the inner film airbagand outer film airbag taken within circle 71A of FIG. 71 but showing analternate configuration where the outer airbag layer has been replacedby a net.

FIG. 71C is an enlarged view of the material of the inner film airbaglayer and outer film airbag layer taken within circle 71A of FIG. 1 butshowing an alternate configuration where fibers of an elastomer areincorporated into an adhesive layer between the two film layers.

FIG. 71D is a perspective view with portions cut away of a vehicleshowing the driver airbag of FIG. 71 mounted on the steering wheel andinflated.

FIG. 72 illustrates a section of a seam area of an airbag showing thedeformation of the elastic sealing film layer.

FIG. 73 is a partial cutaway perspective view of a driver side airbagmade from plastic film.

FIG. 74A is a partial cutaway perspective view of an inflated driverside airbag made from plastic film and a fabric to produce a hybridairbag.

FIG. 74B is a partial cutaway perspective view of an inflated driverside airbag made from plastic film and a net to produce a hybrid airbag.

FIG. 74C is a partial cutaway perspective view of an inflated driverside airbag made from plastic film having a variable thicknessreinforcement in a polar symmetric pattern with the pattern on theinside of the airbag leaving a smooth exterior.

FIG. 74D is an enlarged cross sectional view of the material of the filmairbag taken at 74D-74D of FIG. 74C showing the thickness variationwithin the film material.

FIG. 75A is a partial cutaway perspective view of an inflated driverside airbag made from plastic film using a blow molding process.

FIG. 75B is a partial cutaway perspective view of an inflated driverside airbag made from plastic film using a blow molding process so thatthe airbag design has been partially optimized using finite elementairbag model where the wrinkles have been eliminated and where thestresses within the film are more uniform.

FIG. 75C is a cutaway view of an inflated driver side airbag made fromplastic film showing a method of decreasing the ratio of thickness toeffective diameter.

FIG. 75D is a view of a driver side airbag of FIG. 75C as viewed alongline 75D-75D.

FIG. 76 shows a deployed airbag, supported on the steering wheel of avehicle with a steep steering column, in contact with an occupant.

FIG. 77 shows an inflated airbag and a steering wheel, self-aligned withan occupant.

FIG. 78 shows a driver side airbag module supported by a steeringcolumn, but not attached to the steering wheel.

FIG. 79 illustrates an inflated driver side airbag installed on thedashboard of a vehicle.

FIG. 80 shows an airbag system installed on the dashboard of a vehiclewith a vent hole to the engine compartment.

FIGS. 81A and 81B show a tubular inflatable system mounted on thedashboard of a vehicle.

FIG. 82 is a partial cutaway perspective view of a passenger side airbagmade from plastic film.

FIG. 83 is a perspective view with portions cut away of a vehicleshowing the knee bolster airbag in an inflated condition mounted toprovide protection for a driver.

FIG. 84 is a perspective view of an airbag and inflator system where theairbag is formed from tubes.

FIG. 85 is a perspective view with portions removed of a vehicle havingseveral deployed film airbags.

FIG. 86 is a view of another preferred embodiment of the invention shownmounted in a manner to provide protection for a front and a rear seatoccupant in side impact collisions and to provide protection againstimpacts to the roof support pillars in angular frontal impacts.

FIG. 86A is a view of the side airbag of FIG. 9 of the side airbag withthe airbag removed from the vehicle.

FIG. 87 is a partial view of the interior driver area of a vehicleshowing a self-contained airbag module containing the film airbag ofthis invention in combination with a stored gas inflator.

FIG. 88 is a view looking toward the rear of the airbag module of FIG.87 with the vehicle removed taken at 88-88 of FIG. 87.

FIG. 88A is a cross sectional view of the airbag module of FIG. 88 takenat 88A-88A.

FIG. 88B is a cross sectional view, with portions cutaway and removed,of the airbag module of FIG. 88 taken at 88B-88B.

FIG. 88C is a cross sectional view of the airbag module of FIG. 88 takenat 88C-88C.

FIG. 88D is a cross sectional view of the airbag module of FIG. 88Ataken at 88D-88D.

FIG. 89 is a perspective view of another preferred embodiment of theinvention shown mounted in a manner to provide protection for a frontand a rear seat occupant in side impact collisions, to provideprotection against impacts to the roof support pillars in angularfrontal impacts and to offer some additional protection against ejectionof the occupant or portions of the occupant.

FIG. 90 is a side view of the interior of a motor vehicle provided withanother form of safety device in accordance with the invention, beforethe safety device moves to the operative state.

FIG. 91 illustrates the vehicle of FIG. 90 when the safety device is inthe operative state.

FIG. 92 is a sectional view of one form of safety device as shown inFIGS. 90 and 91 in a plane perpendicular to the vertical direction.

FIG. 92A is a view as in FIG. 92 with additional sheets of materialattached to span the cells.

FIG. 93 is a side view of the passenger compartment of a vehicle showingthe compartment substantially filled with layers of tubular film airbagssome of which are interconnected.

FIG. 93A is a top view of the airbag arrangement of FIG. 93 taken alongline 93A-93A.

FIG. 94 is a similar but alternate arrangement of FIG. 93.

FIG. 95 is another alternate arrangement to FIG. 93 using airbags thatexpand radially from various inflators.

FIG. 96 is a detail of the radial expanding tubular airbags of FIG. 95.

FIG. 96A is an end view of the airbags of FIG. 96 taken along line96A-96A.

FIG. 97 is a detailed view of a knee bolster arrangement in accordancewith the invention.

FIG. 97A illustrates the deployment stages of the knee bolsterarrangement of FIG. 97.

FIGS. 98A, 98D, 98F, 98H, 98J and 98L illustrate various common fabricairbag designs that have been converted to film and have additional filmlayers on each of the two sides of the airbag.

FIGS. 98B, 98C, 98E, 98G, 981, 98K and 98M are cross-sectional views ofFIGS. 98A, 98D, 98F, 98H, 98J and 98L.

FIG. 99 is a perspective view of a self limiting airbag system includinga multiplicity of airbags surrounded by a net, most of which has beencutaway and removed, designed to not cause injury to a child in arear-facing child seat.

FIG. 100 is a partial cutaway perspective view of a driver side airbagmade from plastic film having a variable vent in the seam of the airbag.

FIG. 100A is an enlargement of the variable vent of FIG. 100 taken alongline 100A-100A of FIG. 100.

FIG. 101 shows a plot of the chest acceleration of an occupant and theoccupant motion using a conventional airbag.

FIG. 102 shows the chest acceleration of an occupant and the resultingoccupant motion when the variable orifice of this invention is utilized.

FIG. 103 is a sketch of a first embodiment of a valve in accordance withthe invention.

FIG. 103A is an enlarged view of the portion designated 103A in FIG.103.

FIG. 103B is an alternative actuating device for the embodiment shown inFIG. 103A.

FIG. 104 is a sketch of a second embodiment of a valve in accordancewith the invention.

FIG. 104A is a top view of the embodiment shown in FIG. 104.

FIG. 104B is an enlarged view of the portion designated 104B in FIG.104A.

FIG. 105 is a sketch of a third embodiment of a valve in accordance withthe invention.

FIG. 105A is an enlarged view of the portion designated 105A in FIG.105.

FIG. 106 is a sketch of a fourth embodiment of a valve in accordancewith the invention.

FIG. 106A is a partial cross-sectional view of the embodiment shown inFIG. 106.

FIG. 106B is a top view of the embodiment shown in FIG. 106.

FIG. 107 is a sketch of a fifth embodiment of a valve in accordance withthe invention.

FIG. 107A is a partial cross-sectional view of the embodiment shown inFIG. 107.

FIG. 107B is a top view of the embodiment shown in FIG. 107.

FIG. 108 is a sketch of a sixth embodiment of a valve in accordance withthe invention.

FIG. 108A is a partial cross-sectional view of the embodiment shown inFIG. 108.

FIG. 108B is a top view of the embodiment shown in FIG. 108.

FIG. 109 is a sketch of a seventh embodiment of a valve in accordancewith the invention.

FIG. 109A is a partial cross-sectional view of the embodiment shown inFIG. 109.

FIG. 109B is a top view of the embodiment shown in FIG. 109.

FIGS. 110A and 110B are sketches of variations of a valve in accordancewith the invention showing the use of a cylinder valve.

FIGS. 111A and 111B are sketches of variations of a valve in accordancewith the invention showing the use of a cone-shaped valve.

FIG. 112 is an illustration of a discharge valve including stacked driveelements.

FIG. 113 is a “Cussler” model graph indicating the effective aspectratios achieved by compositions of this invention. The graph plotsreduction of permeability vs. volume percentages of filler in barriercoating mixtures of the present invention. Cussler describes severalmodels for the permeability reduction due to oriented layered fillers,which depend on the microstructure expected. For simplicity, thisinvention employs the equation: Pu/P=[1+(a2X2)/(1−X)]/(1−X), where P isthe permeability of the filled material, Pu is the permeability of theunfilled material; a is the aspect ratio of the filler particles; X isthe volume fraction of the filler particles in the coating. Cussler'stheoretical curves for fillers with aspect ratios of 25, 50, 75, and 100are present on the graph. The thick “experimental” data line records theexperimental data points for the barrier coating mixtures of Examples1-8 below. Effective aspect ratios can be estimated from the position ofthe data relative to the theoretical curves.

FIG. 114 is a graph plotting permeability results based on the weightpercentage of a filler, vermiculite. Permeability is plotted vs. weight% of filler. Increase in weight % of filler decreases the permeabilityof the coating.

FIG. 115 is a graph plotting reduction in permeability vs. weight % offiller in coating. Increase in weight % of filler increases thereduction of permeability.

FIGS. 116 and 117 are graphs illustrating the maximum percentage solidsand butyl latex (BL100™) to filler ratio vs. percentage by weight ofMICROLITE® vermiculite in coating compositions of the invention.

FIG. 118 illustrates flexibility data at 10% elongation, 1 K cyclesbased on the flex test of Example 17.

FIG. 119 is a schematic view of a vehicle with portions cutaway showingan airbag module including an airbag in accordance with the invention inthe ceiling of the vehicle.

FIG. 120 is a partial cross section of a vehicle passenger compartmentillustrating a curtain airbag in the folded condition prior todeployment.

FIG. 121 is an enlarged view of airbag module shown in FIG. 120.

FIGS. 122A and 122B are cross-sectional views taken along the line122-122 in FIG. 121.

FIG. 123 is a flow chart of a method for designing a side curtain airbagin accordance with the invention.

FIG. 124 is an illustration of a side curtain airbag device with anaspirated inflator located on one end in contrast to FIG. 53H where theaspiration takes place along the entire module.

FIG. 124A is an enlarged view of the section designated 124A in FIG.124.

FIG. 125 shows an alternative elongate inflator for use as a thindistributed inflator for side curtain airbags for mounting on the roofrail.

FIG. 125A is a cross-sectional view taken along the line 125A-125A inFIG. 125.

FIGS. 126A and 126B show aspirated driver side steering wheel-mountedaspirated inflators and airbag modules for a non rotating inflator.

FIGS. 127A and 127B show aspirated driver side steering wheel-mountedaspirated inflators and airbag modules where the inflator rotates withthe airbag module.

FIGS. 128 and 129 are views of examples of collected images of vehiclesused for object recognition.

FIG. 130 shows the result of an edge discrimination algorithmapplication.

FIGS. 131 and 132 show examples of the image segmentation algorithm oncars and trucks, respectively.

FIG. 133 shows examples of inaccuracies in the edge discriminationalgorithm.

FIG. 134 shows an example of binary images or a car and truck.

FIG. 135 shows a chart of the pressure in a compressed-airflask/pressure in an airbag vs. the ratio of the airbag's volume andthat of the flask.

FIG. 136 shows a typical shape of a central-body inflator.

FIG. 137 shows a calculated result for a characteristic velocity fieldin the inflator after the steady state is achieved.

FIG. 138 shows drawings of the plane inflators, batches A1-A5, and somemodifications tested.

FIG. 139 shows the inflator of batch A1.

FIG. 140 shows the appearance of the inflator A5 assembled with a bag,electromagnetic air-valves and sensors.

FIGS. 141A and 141B show pressure and velocity profiles across themixing chamber in the location after the slot exit where high-speed jetmixes with free air flow from inside a vehicle.

FIG. 141C shows calculated pressure distribution along the wall of theinflator.

FIG. 142 shows pressure (negative value) measured at the locations L,G,Rof FIG. 136 during the period when the high-pressure valve is open.

FIG. 143 shows calculation results and measured data for volumetricrate.

FIG. 144 shows the aspiration ratio, in dependence on boost pressure inthe inflator A1-1.

FIG. 145 shows calculation results and measured data for volumetric ratewith a change in the size and shape of the mixing chamber.

FIG. 146 shows the aspiration ratio, in dependence on boost pressure inthe inflator A1-1 for the changed mixing chamber.

FIG. 147 shows the aspiration ratio, in dependence on boost pressure ina modified inflator A2-4.

FIG. 148 shows test modification.

FIGS. 149 and 150 shows test results for inflator A5.

FIG. 151 shows an inflator without a central body.

FIG. 152 shows a calculated result for a characteristic velocity fieldin the inflator of FIG. 151 after the steady state is achieved.

FIG. 153 shows the inflator A6 assembled with a bag and electromagneticair-valves.

FIGS. 154 and 155 show measured data for modifications to inflator A6.

FIGS. 156 and 157 show calculation results of total flow rate andaspiration ratio in different inflators vs. high static pressure in theflask that generates the high-speed jet.

FIG. 158 shows experimentally measured flow rates for differentmodifications of inflators from batches A0-A6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

1 Crash Sensors

1.1 Pattern Recognition Approach to Crash Sensing

Throughout much of the discussion herein, the neural network will beused as an example of a pattern recognition technique or algorithm sincethe neural network is one of the most developed of such techniques.However, it has limitations that are now being addressed with thedevelopment of newer pattern recognition techniques as well as betterneural network techniques such as combination or modular neuralnetworks. These limitations involve the difficulty in describing theprocess used in classifying patterns with the result that there is afear that a pattern that was not part of the training set might bemissed. Also, the training process of the neural network does notguarantee that convergence to the best solution will result. One suchexample is the local minimum problem wherein the training algorithmconverges on a result that is not the best overall or global solution.These problems are being solved with the development of newer patternrecognition techniques such as neural networks, regardless of theparticular technique, to provide a superior smart airbag system. Inparticular, genetic algorithms are being applied to aid in selecting thebest of many possible choices for the neural network architecture. Theuse of genetic algorithms helps avoid the local minimum situationmentioned above since several different architectures are tried and thebest retained.

The pattern recognition algorithm, which forms an integral part of thecrash sensor described herein, can be implemented either as an algorithmusing a conventional microprocessor, FPGA or ASIC or through a neuralcomputer. In the first case, the training is accomplished using a neuralpattern recognition program and the result is a computer algorithmfrequently written in the C computer language, although many othercomputer languages such as FORTRAN, assembly, Basic, etc. could be used.In the last case, the same neural computer can be used for the trainingas used on the vehicle. Neural network software for use on aconventional microcomputer is available from several sources such asInternational Scientific Research, Panama City, Panama. An example of aneural network-based crash sensor algorithm produced by ISR softwareafter being trained on a crash library created by using data supplied byan automobile manufacturer for a particular model vehicle plusadditional data created by using the techniques of crash and velocityscaling is:

* Neural net for crash sensor. 23 August 94. 50 input nodes, * 6 hiddennodes (sigmoid transfer function), 1 output node (value 0 or 1). *Network was trained using back propagation with Logicon Projection. *Yin(1-50) are raw input values. Xin(1-50) are scaled input values. *Yin(50) is the sum of the latest 25 accelerations, in tenths of a g, *Yin(49) is the sum of the previous 25, etc. The time step is 80microsecond. logical function nnmtlpn3( Yin, firesum, Yout ) real*4firesum, Yin(50), Yout  integer i, j real*4 biashid(6), biasout,fire_criterion, hiddenout(6), NormV, NV(4), & offset_in(50), offset_out,scale_in(50), scale_out, wgthid(51,6), & wgtout(6), Xin(51), Xsum parameter( fire_criterion = 0.0 ) data scale_in/ (omitted) /   dataoffset_in/ (omitted) /  data scale_out, offset_out / 0.625, 0.5 /   dataNV/ 2.0, 7.0, 7.0711002, 50.000458 /  data biashid/ −49.110764,−69.856407, −48.670643,  & −48.36599, −52.745285, −49.013027 /  databiasout/ 0.99345559 /  data wgthid/ (omitted) /   data wgtout/ (omitted)/  NormV = 0.0  do i=1,50  Xin(i) = scale_in(i) * Yin(i) − offset_in(i) NormV = NormV + Xin(i) * Xin(i)  enddo   NormV = NV(1) * NV(2) * NV(3)/ ( NV(4) + NormV )   do i=1,50  Xin(i) = NormV * Xin(i)  enddo  Xin(51) = NV(2) − NV(3) * NormV  do i=1,6  Xsum = biashid(i)  doj=1,51   Xsum = Xsum + wgthid(j,i) * Xin(j)  enddo  hiddenout(i) = 1.0 /( 1.0 + exp( −Xsum ) )  enddo  firesum = biasout  do i=1,6  firesum =firesum + wgtout(i) * hiddenout(i)  enddo   Yout = offset_out +scale_out * tanh(firesum)   if( firesum .GE. fire_criterion ) then nnmtlpn3 = .TRUE.  else  nnmtlpn3 = .FALSE.  endif  return end

Neural computers on a chip are now available from various chipsuppliers. These chips make use of massively parallel architecture andallow all of the input data to be processed simultaneously. The resultis that the computation time required for a pattern to be tested changesfrom the order of milliseconds for the case of themicroprocessor-implemented system to the order of tens to hundreds ofmicroseconds for the neural computer. With this computational speed, oneneural computer can easily be used for several pattern recognitionimplementations simultaneously even during the crash event includingdynamic out-of-position and crash sensing. A discussion of the structureof such a neural computer can be found on page 382 of Digital NeuralNetworks, by Kung, S. Y., PTR Prentice Hall, Englewood Cliffs, N.J.,1993.

An example of an algorithm produced by such software after being trainedon a crash library created by using data supplied by an automobilemanufacturer for a particular model vehicle plus additional data createdby using the techniques of crash and velocity scaling is illustratedabove. In this case, the network was trained to give a value of 1 fortriggering the airbag and 0 for not triggering. In the instant case,this value would depend on the type of gas control module that is usedand in general would vary continuously from 0 to 1 with the particularvalue indicative of the action to be taken by the gas control module,such as adding more gas to the airbag.

Examples of neural networks in several forms will be discussed in moredetail below in several sections of this application.

1.2 Electronic Crash Sensors

An airbag electronic sensor and diagnostic module (SDM) is typicallymounted at a convenient location in the passenger compartment such asthe transmission tunnel or firewall. FIG. 1 is a view of the front of apassenger compartment 50 of an automobile with portions cut away andremoved, having dual airbags 51, 52 and an SDM 55 containing a non crushzone electronic crash sensor and crash forecasting algorithm,(hereinafter this combination will be referred to as a crash sensor)comprising one to three accelerometers and zero to three gyroscopes 56,one or more analog to digital converters (ADC) 57 and a patternrecognition algorithm contained within a microprocessor 59, all of whichmay be mounted on a single circuit board and electrically coupled to oneanother (see FIG. 1A). Alternately, the microprocessor 59 can be aneural computer.

A tri-axial accelerometer is a device that includes three accelerometersand measures accelerations in three orthogonal directions that aretypically the longitudinal, lateral and vertical directions, althoughthere are sometimes reasons to use a different orientation. Such adifferent orientation can be useful to remove some of the bias errors inthe accelerometers by, for example, allowing each accelerometer to bepartially influenced by gravity. Also, in some applications, thetri-axial accelerometer is intentionally rotated relative to the vehicleto expose different accelerometers to gravity again for accuracycalibration purposes. An alternate method is to electronically test theacceleration sensing elements by exposing them to an electric field andmeasure their response. Such an accelerometer is called a “testable”accelerometer.

The circuit board of the SDM 55 also optionally contains a capacitor 61as a backup power supply, other electronic components 58 and variouscircuitry. The SDM is connected to the airbags 51, 52 with wires 53 and54 (shown in dotted lines in FIG. 1), although a wireless electricalconnection is also a possibility as wireless data transfer has becomemore reliable. In this embodiment, the pattern recognition techniqueused is a neural network that analyzes data from one, two or threeaccelerometers, and optionally up to three gyroscopes, to determinewhether the vehicle is experiencing a crash from any direction.Alternately, an IMU may be used. If the neural network determines, e.g.,by analysis of a pattern in the signals emanating from theaccelerometer(s) 56 and gyroscope(s) 56, that the accident meritsdeployment of one or more protection or restraint systems, such as aseatbelt retractor, frontal or side airbag, or a movable headrest, itinitiates such deployment and thus constitutes in this regard airbagdeployment initiation means. It also may determine the settings for anairbag inflation/deflation control module which determines how much gasis to be generated, how fast it is to be generated, how much should befed into the airbag, how much should be dumped to the atmosphere and/orhow much should be permitted to exhaust from the airbag. The particularmethod and apparatus for controlling the flows of gas into and/or out ofthe airbag will depend on the particular system design. The controllerfor any such system will hereinafter be referred to as the gas controlmodule and is illustrated in FIG. 1A schematically as 60.

For frontal impacts, for example, a signal is sent through wires 53 and54 to initiate deployment of airbags 51 and 52 and to control the gasflow into and/or out of each airbag 51, 52 through the gas controlmodules (not shown) for each airbag. The ADC 57 is connected to theacceleration sensor, in this case the tri-axial accelerometer 56, andconverts an analog signal generated by one or more of the accelerometers56 representative of the acceleration thereof, and thus the vehicle,into a digital signal. In one embodiment, the ADC 57 may derive thedigital signal from the integral of the analog signal. Naturally, manyof the components of the printed circuit board can be incorporated intoan ASIC as is obvious to those skilled in the art.

The tri-axial accelerometer and/or gyroscopes 56 (or IMU) are mounted bysuitable mounting structure to the vehicle and can be mounted in avariety of positions to sense, e.g., frontal impacts, side impacts, rearimpacts and/or rollovers. In another embodiment described below, themicroprocessor 59 may include a detection system for detecting when theoccupant to be protected by the deployable airbags 51, 52 isout-of-position and thereupon to suppress deployment thereof. Also, thedetection system may be applied to detect the presence of a rear-facingchild seat positioned on a passenger seat and thereupon to suppressdeployment of the airbag. In each case, the microprocessor or neuralcomputer 59 performs an analysis on signals received from appropriatesensors and corresponding ADCs. Recent advances in computational theorysuggest that a form of computation using analog data rather than digitaldata may become viable. One example is the use of optical correlatorsfor object detection and identification in the military where theoptical signal from a video scene is converted to its Fourier transformusing diffraction techniques.

The pattern recognition crash sensor described and illustrated in FIGS.1 and 1A is capable of using information from three accelerometers 56,for example, each measuring acceleration from an orthogonal direction.As will be described in more detail below, other information can also beconsidered by the pattern recognition algorithm such as the position ofthe occupants, noise, data from anticipatory acoustic, radar, infraredor other electromagnetic sensors, seat position sensors, seatbeltsensors, speed sensors, gyroscopes or any other information present inthe vehicle which is relevant. Since the pattern recognition algorithmis trained on data from real crashes and non-crash events, it can handledata from many different information sources and sort out what patternscorrespond to airbag-required events in a way that is nearly impossiblefor an engineer to do. For this reason, a crash sensor based on neuralnetworks, for example, will invariably perform better than one devisedby engineers. The theory of neural networks including many examples canbe found in several books on the subject including: Techniques andApplication of Neural Networks, edited by Taylor, M. and Lisboa, P.,Ellis Horwood, West Sussex, England, 1993; Naturally IntelligentSystems, by Caudill, M. and Butler, C., MIT Press, Cambridge Mass.,1990; J. M. Zaruda, Introduction to Artificial Neural Systems, WestPublishing Co., N.Y., 1992 and, Digital Neural Networks, by Kung, S. Y.,PTR Prentice Hall, Englewood Cliffs, N.J., 1993, Eberhart, R., Simpson,P. and Dobbins, R., Computational Intelligence PC Tools, Academic Press,Inc., 1996, Orlando, Fla. The neural network pattern recognitiontechnology is one of the most developed of pattern recognitiontechnologies. Newer and more efficient systems are now being developedsuch as the neural network system which is being developed by Motorolaand is described in U.S. Pat. Nos. 5,390,136 and 5,517,667. The neuralnetwork will be used here to illustrate one example of a patternrecognition technology but it is emphasized that this invention is notlimited to neural networks. Rather, the invention may apply any knownpattern recognition technology. A brief description of the neuralnetwork pattern recognition technology is set forth below.

A diagram of one example of a neural network used for a crash sensordesigned based on the teachings of this invention is shown in FIG. 2.The process can be programmed to begin when an event occurs whichindicates an abnormal situation such as the acceleration in thelongitudinal direction, for example, exceeding the acceleration ofgravity, or it can take place continuously depending on the demands onthe computer system. The digital acceleration values from the ADC 57 maybe pre-processed, for example by filtering, and then enteredsuccessively into nodes 1, 2, 3, . . . , N (this entry represented bythe arrows) and the neural network algorithm compares the pattern ofvalues on nodes 1 through N with patterns for which it has been trained.Each of the input nodes is connected to each of the second layer nodesh-1, . . . , h-n, called the hidden layer, either electrically as in thecase of a neural computer, to be described below, or throughmathematical functions containing multiplying coefficients calledweights, also described in more detail below. The weights are determinedduring the training phase while creating the neural network as describedin detail in the above text references. At each hidden layer node, asummation occurs of the values from each of the input layer nodes, whichhave been operated on by functions containing the weights, to create anode value. Similarly, the hidden layer nodes are connected to theoutput layer nodes O-1, O-2, . . . , O-n, which can be only a singlenode representing the control parameter to be sent to the gas controlmodule, for example. If this value exceeds a certain threshold, the gascontrol module initiates deployment of the airbag.

During the training phase, an output node value is assigned for everysetting of the gas control module corresponding to the desired gas flowfor that particular crash as it has occurred at a particular point intime. As the crash progresses and more acceleration values appear on theinput nodes, the value of the output node may change. In this manner, aslong as the crash is approximately represented in the training set, thegas flow can be varied at each one or two milliseconds depending on thesystem design to optimally match the quantity of gas in the airbag tothe crash as it is occurring. Similarly, if an occupant sensor and aweight sensor are present, that information can additionally be fed intoa set of input nodes so that the gas module can optimize the quantity ofgas in the airbag taking into account both the crash deceleration andalso the position, velocity, size and/or weight of the occupant tooptimally deploy the airbag to minimize airbag induced injuries andmaximize the protection to the occupant. Details of the manner in whicha neural network process operates and is trained are described inabove-referenced texts and will not be presented in detail here.

A time step, such as two milliseconds, is selected as the period inwhich the ADC pre-processes the output from the accelerometers and feedsdata to input node 1. Thus, using this time step, at time equal to 2milliseconds from the start of the process, node 1 contains a valueobtained from the ADC and the remaining input nodes have a random valueor a value of 0. At time equal 4 milliseconds, the value that was onnode 1 is transferred to node 2 (or the node numbering scheme isadvanced) and a new value from the ADC is fed into node 1. In a similarmanner, data continues to be fed from the ADC to node 1 and the data onnode 1 is transferred to node 2 whose previous value was transferred tonode 3 etc. The actual transfer of data to different memory locationsneed not take place but only a redefinition of the location that theneural network should find the data for node 1. For one preferredembodiment of this invention, a total of one hundred input nodes wereused representing two hundred milliseconds of acceleration data. At eachstep, the neural network is evaluated and if the value at the outputnode exceeds some value such as 0.5, then the airbags are deployed bythe remainder of the electronic circuit. In this manner, the system doesnot need to know when the crash begins, that is, there is no need for aseparate sensor to determine the start of the crash or of a particularalgorithm operating on the acceleration data to make that determination.

In the example above, one hundred input nodes were used, along withtwelve hidden layer nodes and one output layer node. Accelerations fromonly the longitudinal direction were considered. If other data such asaccelerations from the vertical or lateral directions or the output froma number of gyroscopes were also used, then the number of input layernodes would increase. If the neural network is to be used for sensingrear impacts, or side impacts, 2 or 3 output nodes might be used, onefor each gas control module, headrest control module etc. Alternately,combination, modular or even separate neural networks can be used. Thetheory for determining the complexity of a neural network for aparticular application is the subject of many technical papers and willnot be presented in detail here. Determining the requisite complexityfor the example presented herein can be accomplished by those skilled inthe art of neural network design and is discussed briefly below. Inanother implementation, the integral of the acceleration data is usedand it has been found that the number of input nodes can besignificantly reduced in this manner.

The neural network described above defines a method of sensing a crashand determining whether to begin inflating a deployable occupantprotection device, and at what rate, and comprises:

(a) obtaining one or more acceleration signals from one or moreaccelerometers mounted on a vehicle;

(b) converting the acceleration signal(s) into a digital time serieswhich may include pre-processing of the data;

(c) entering the digital time series data into the input nodes of aneural network;

(d) performing a mathematical operation on the data from each of theinput nodes and inputting the operated-on data into a second series ofnodes wherein the operation performed on each of the input node dataprior to inputting the operated on value to a second series node isdifferent from that operation performed on some other input node data;

(e) combining the operated-on data from all of the input nodes into eachsecond series node to form a value at each second series node;

(f) performing a mathematical operation on each of the values on thesecond series of nodes and inputting the operated-on data into an outputseries of nodes wherein the operation performed on each of the secondseries node data prior to inputting the operated on value to an outputseries node is different from that operation performed on some othersecond series node data;

(g) combining the operated on data from all of the second series nodesinto each output series node to form a value at each output series node;and,

(h) initiating gas flow into an airbag if the value on one output seriesnode is within a selected range signifying that a crash requiring thedeployment of an airbag is underway; and

(i) causing the amount of gas flow into or out of the airbag to dependon the value on that one output series node.

The particular neural network described and illustrated above contains asingle series of hidden layer nodes. In some network designs, more thanone hidden layer is used although only rarely will more than two suchlayers appear. There are of course many other variations of the neuralnetwork architecture illustrated above which appear in the literature.

The implementation of neural networks can have at least two forms, analgorithm programmed on a digital microprocessor or in a neuralcomputer. Neural computer chips are now available and neural computerscan be incorporated into ASIC designs. As more advanced patternrecognition techniques are developed, specially designed chips can beexpected to be developed for these techniques as well.

FIG. 3 provides the results of a neural network pattern recognitionalgorithm, as presented in U.S. Pat. No. 5,684,701 referenced above, foruse as a single point crash sensor. The results are presented for amatrix of crashes created according to the velocity and crash scalingtechniques presented in the above-referenced papers (1-13). The tablecontains the results for different impact velocities (vertical column)and different crash durations (horizontal row). The results presentedfor each combination of impact velocity and crash duration consist ofthe displacement of an unrestrained occupant at the time that airbagdeployment is initiated and 30 milliseconds later. This is presentedhere as an example of the superb results obtained from the use of aneural network crash sensor that forms a basis of the instant invention.In FIG. 3, the success of the sensor in predicting that the velocitychange of the accident will exceed a threshold value is demonstrated. Inthe instant invention, this capability is extended to where theparticular severity of the accident is (indirectly) determined and thenused to set the flow of gas into and/or out of the airbag to optimizethe airbag system for the occupant and the crash severity.

Airbags have traditionally been designed based on the assumption that 30milliseconds of deployment time is available before the occupant, asrepresented by an unbelted dummy corresponding to the average male, hasmoved five inches. An occupant can be seriously injured or even killedby the deployment of the airbag if he or she is too close to the airbagwhen it deploys and in fact many people, particularly children and smalladults, have now been killed in this manner. It is known that this isparticularly serious when the occupant is leaning against the airbagwhen it deploys which corresponds to about 12 inches of motion for theaverage male occupant, and it is also known that he will be uninjured bythe deploying airbag when he has moved less than 5 inches when theairbag is completely deployed. These dimensions are based on the dummythat represents the average male, the so-called 50% male dummy, sittingin the mid-seating position.

The threshold for significant injury is thus somewhere in between thesetwo points and thus for the purposes of this table, two benchmarks havebeen selected as being approximations of the threshold of significantinjury. These benchmarks are, based on the motion of an unrestrainedoccupant, (i) if the occupant has already moved 5 inches at the timethat deployment is initiated, and (ii) if the occupant has moved 12inches by the time that the airbag is fully deployed. Both benchmarksreally mean that the occupant will be significantly interacting with theairbag as it is deploying. Other benchmarks could of course be used;however, it is believed that these two benchmarks are reasonable lackinga significant number of test results to demonstrate otherwise, at leastfor the 50% male dummy.

The tables shown in FIGS. 3 and 4, therefore, provide data as to thedisplacement of the occupant relative to the airbag at the time thatdeployment is initiated and 30 milliseconds later. If the first numberis greater than 5 inches or the second number greater than 12 inches, itis assumed that there is a risk of significant injury and thus thesensor has failed to trigger the airbag in time. For these cases, thecell in the table has been shaded. As can be seen in FIG. 3, whichrepresents the neural network crash sensor designed according to theteachings of this invention, none of the cells are shaded so theperformance of the sensor is considered excellent.

The table shown in FIG. 4 represents a model of a single point crashsensor used on several production vehicle models in use today. In fact,it was designed to be optimized for the crashes shown in the table. Asshown in FIG. 4, the sensor fails to provide timely airbag deployment ina significant percentage of the crashes represented in the table. Sincethat sensor was developed, several manufacturers have developed crashsensor algorithms by trial and error that probably perform better thanthat which would provide the results shown in FIG. 4. It is not possibleto ascertain the success of these improved sensors since the algorithmsare considered proprietary. Note, the figures used including the 50%male, 30 milliseconds and travel distances of 5 and 12 inches areassumptions and simplifications that are not necessary once occupantsensors are installed in vehicles.

One additional feature, which results from the use of the neural networkcrash sensor of this invention, is that at the time the decision is madeto deploy the airbag and even for as long afterward as the sensor isallowed to run, in the above example, 200 milliseconds of crash data isstored in the network input nodes. This provides a sort of “black box”which can be used later to accurately determine the severity of thecrash as well as the position of the occupant at the time of the crash.IIf some intermediate occupant positions are desired, they could bestored on a separate non-volatile memory.

Above, the sensing of frontal impacts has been discussed using a neuralnetwork derived algorithm. A similar system can be derived for rear andside impacts especially if an anticipatory sensor is available as willbe discussed below. An IMU located at a single location in a vehicle cando an excellent job of monitoring the motions of the vehicle that couldlead to accidents including pre-crash braking, excessive yaw or pitchingor roll which could lead to a rollover event. If the vehicle also has aGPS system, then the differential motion of the vehicle over a period ofone second as measured by the GPS can be used to calibrate the IMUeliminating all significant errors. This is done using a Kalman filter.If a DGPS system is also available along with an accurate map, then thevehicle will also know its precise position within centimeters. Thishowever is not necessary for calibrating and thereby significantlyimproving the accuracy of the IMU and thus the vehicle motion can beknown approximately 100 times better than systems that do not use such aGPS-calibrated IMU. This greatly enhances the ability of vehicle systemsto avoid skidding, rollover and other out-of-control situations thatfrequently lead to accidents, injuries and death. This combination of aninexpensive perhaps MEMS-based IMU with GPS and a Kalman filter haspreviously not been applied to a vehicle for safety and vehicle controlpurposes although the concept has been used with a DGPS system for farmtractors for precision farming.

With an accurate IMU, as mentioned above, the weight of a variablyloaded vehicle can be determined and sent by telematics to a weighstation thereby eliminating the need for the vehicle to stop and beweighed.

Such an accurate IMU can also be used to determine the inertialproperties of a variably loaded vehicle such as a truck or trailer. Inthis case, the IMU output can be analyzed by appropriate equations of aneural network, and with assumed statistical road properties plusperhaps some calibration for a particular vehicle, to give the center ofmass of the vehicle as well as its load and moments of inertia. Withthis knowledge plus even a crude digital map, a driver can be forewarnedthat he might wish to slow down due to an upcoming curve. If telematicsare added, then the road properties can be automatically accumulated atan appropriate off-vehicle location and the nature of the road under allweather conditions can be made available to trucks traveling the road tominimize the chance of accidents. This information plus the output ofthe IMU can significantly reduce truck accidents. The information canalso be made available to passing automobiles to warn them of impendingpotential problems. Similarly, if a vehicle is not behavingappropriately based on the known road geometry, for example if thedriver is wandering off the road, traveling at an excessive speed forconditions or generally driving in an unsafe manner, the off-vehiclesite can be made aware of the fact and remedial action taken.

There are many ways to utilize one or more IMUs to improve vehiclesafety and in particular to prevent rollovers, out-of-control skidding,jack-knifing etc. In a simple implementation, a single IMU is placed atan appropriate location such as the roof of a truck or trailer and usedto monitor the motion over time of the truck or trailer. Based on theassumption that the road introduces certain statistically determinabledisturbances into the vehicle, such monitoring over time can give a goodidea of the mass of the vehicle, the load distribution and its momentsof inertia. It can also give some idea as to the coefficient of frictionon the tires against the roadway. If there is also one or more IMUslocated on the vehicle axle or other appropriate location that moveswith the wheels, then a driving function of disturbances to the vehiclecan also be known leading to a very accurate determination of theparameters listed above especially if both a front and rear axle are soequipped. This need not be prohibitively expensive as IMUs are expectedto break the $100 per unit level in the next few years.

As mentioned above, if accurate maps of information from other vehiclesare available, the IMUs on the axles may not be necessary as the drivingfunction would be available from such sources. Over the life of thevehicle, it would undoubtedly be driven empty and full to capacity sothat if an adaptive neural network is available, the system cangradually be trained to quickly determine the vehicle's inertialproperties when the load or load distribution is changed. It can also betrained to recognize some potentially dangerous situations such as loadsthat have become lost resulting in cargo that shifts during travel.

If GPS is not available, then a terrain map can also be used to providesome corrections to the IMU. By following the motion of the vehiclecompared with the known geometry of the road, a crude deviation can bedetermined and used to correct IMU errors. For example, if the beginningand end of a stretch of a road is known and compared with the integratedoutput of the IMU, then corrections to the IMU can be made.

The MEMS gyroscopes used in a typical IMU are usually vibrating tuningforks or similar objects. Another technology developed by the ScirasCompany of Anaheim, Calif., (The μSCIRAS multisensor, a CoriolisVibratory Gyro and Accelerometer IMU) makes use of a vibratingaccelerometer and shows promise of making a low cost gyroscope withimproved accuracy. A preferred IMU is described in U.S. Pat. No.0,471,125. One disclosed embodiment of a side impact crash sensor for avehicle in accordance with the invention comprises a housing, a masswithin the housing movable relative to the housing in response toaccelerations of the housing, and structure responsive to the motion ofthe mass upon acceleration of the housing in excess of a predeterminedthreshold value for controlling an occupant protection apparatus. Thehousing is mounted by an appropriate mechanism in such a position and adirection as to sense an impact into a side of the vehicle. The sensormay be an electronic sensor arranged to generate a signal representativeof the movement of the mass and optionally comprise a microprocessor andan algorithm for determining whether the movement over time of the massas processed by the algorithm results in a calculated value that is inexcess of the threshold value based on the signal. In the alternative,the mass may constitute part of an accelerometer, i.e., a micro-machinedacceleration sensing mass. The accelerometer could include apiezo-electric element for generating a signal representative of themovement of the mass.

An embodiment of a side impact airbag system for a vehicle in accordancewith an invention herein comprises an airbag housing defining aninterior space, one or more inflatable airbags arranged in the interiorspace of the system housing such that when inflating, the airbag(s)is/are expelled from the airbag housing into the passenger compartment(along the side of the passenger compartment), and an inflator mechanismfor inflating the airbag(s). The inflator mechanism may comprise aninflator housing containing propellant. The airbag system also includesa crash sensor as described above for controlling inflation of theairbag(s) via the inflator mechanism upon a determination of a crashrequiring inflation thereof, e.g., a crash into the side of the vehiclealong which the airbag(s) is/are situated. The crash sensor may thuscomprise a sensor housing arranged within the airbag housing, externalof the airbag housing, proximate to the airbag housing and/or mounted onthe airbag housing, and a sensing mass arranged in the sensor housing tomove relative to the sensor housing in response to accelerations of thesensor housing resulting from, e.g., the crash into the side of thevehicle. Upon movement of the sensing mass in excess of a thresholdvalue, the crash sensor controls the inflator to inflate the airbag(s).The threshold value may be the maximum motion of the sensing massrequired to determine that a crash requiring deployment of the airbag(s)is taking place.

The crash sensor of this embodiment, or as a separate sensor of anotherembodiment, may be an electronic sensor and the movement of the sensingmass may be monitored. The electronic sensor generates a signalrepresentative of the movement of the sensing mass that may be monitoredand recorded over time. The electronic sensor may also include amicroprocessor and an algorithm for determining whether the movementover time of the sensing mass as processed by the algorithm results in acalculated value that is in excess of the threshold value based on thesignal.

In some embodiments, the crash sensor also includes an accelerometer,the sensing mass constituting part of the accelerometer. For example,the sensing mass may be a micro-machined acceleration sensing mass inwhich case, the electronic sensor includes a micro-processor fordetermining whether the movement of the sensing mass over time resultsin an algorithmic determined value which is in excess of the thresholdvalue based on the signal. In the alternative, the accelerometerincludes a piezoelectric element for generating a signal representativeof the movement of the sensing mass, in which case, the electronicsensor includes a micro-processor for determining whether the movementof the sensing mass over time results in an algorithmic determined valuewhich is in excess of the threshold value based on the signal.

1.3 Crash Severity Prediction

In the particular implementation described above, the neural networkcould be trained using crash data from approximately 25 crash andnon-crash events. In addition, the techniques of velocity and crashscaling, as described in the above-referenced technical papers, wereused to create a large library of crashes representing many events notstaged by the automobile manufacturer. The resulting library, it isbelieved, represents the vast majority of crash events that occur inreal world accidents for the majority of automobiles. Thus, the neuralnetwork algorithm comes close to the goal of a universal electronicsensor usable on most if not all automobiles as further described inU.S. Pat. No. 5,684,701. The results of this algorithm as reported inthe '701 patent for a matrix of crashes created by the above-mentionedvelocity and crash scaling technique appears in FIGS. 7 and 8 of thatpatent (FIGS. 3 and 4 herein). An explanation of the meaning of thenumbers in the table can be found in reference 2 above.

The '701 patent describes the dramatic improvement achievable throughthe use of pattern recognition techniques for determining whether theairbag should be deployed. Such a determination is really a forecastingthat the eventual velocity change of the vehicle will be above anamount, such as about 12 mph, which requires airbag deployment. Theinstant invention extends this concept to indirectly predict what theeventual velocity change will in fact be when the occupant, representedby an unrestrained mass, impacts the airbag. Furthermore, it does so notjust at the time that the deployment decision is required but also, inthe preferred implementation, at all later times until adding orremoving additional gas from the airbag will have no significant injuryreducing effect. The neural network can be trained to predict orextrapolate this velocity but even that is not entirely sufficient. Whatis needed is to determine the flow rate of gas into and/or out of theairbag to optimize injury reduction which depends not only on theprediction or extrapolation of the velocity change at a particular pointin time but must take into account the prediction that was made at anearlier point when the decision was made to inject a given amount of gasinto the airbag. Also, the timing of when the velocity change will occuris a necessary parameter since gas is usually not only flowing into butout of the airbag and both flows must be taken into account. It is thusunlikely that an algorithm, which will perform well in all real worldcrashes, can be mathematically derived.

The neural network solves the problem by considering all of theacceleration up to the current point in the crash and therefore knowshow much gas has been put into the airbag and how much has flowed out.It can be seen that even if this problem could be solved mathematicallyfor all crashes, the mathematical approach becomes hopeless as soon asthe occupant properties are added.

Once a pattern recognition computer system is implemented in a vehicle,the same system can be used for many other pattern recognition functionssuch as the airbag system diagnostic. Testing that the pattern of theairbag system during the diagnostic test on vehicle startup, asrepresented by the proper resistances appearing across the wires to thevarious system components, for example, is an easy task for a patternrecognition system. The system can thus do all of the functions of theconventional SDM, sensing and diagnostics, as well as many others.

1.4 Crush Zone Mounted Sensors

So far electronic sensors mounted in the passenger compartment forsensing crashes have been considered. It has also been pointed out thatthere is insufficient information in the passenger compartment to senseall crashes in time. The best place to sense a crash is where it ishappening, that is, where the vehicle is crushing and in this section,crush zone sensing will be introduced.

Referring now to FIGS. 5-17, a crush zone mounted sensor constructed inaccordance with the teachings of at least one invention herein for usein sensing frontal impacts is shown generally at 70 in FIG. 5. Thesensor 70 comprises a unitary, tubular member having two verticalportions 84 and 85, a lower horizontal portion 86, two upper horizontalportions 87 and 88 and a rearward projecting portion 89. The sensor 70is closed at an end 71 of horizontal portion 88, e.g., by welding, asdescribed below and a header/connector 72 is attached to the sensor 70at the end of portion 89.

The sensor 70 is mounted to the front of the vehicle as shown in FIG. 7and is constructed of a tube 74 and a centrally located rod 73 as shownin FIG. 6, which is substantially coextensive with the tube 74 butnormally not in contact therewith. The sensor 70 functions (for exampleby initiating airbag deployment) when it is bent at any position alongthe tube 74 with the exception of bent sections or bends 96 which jointhe vertical portions 84, 85 to the upper horizontal portions 87, 88,respectively, and where plastic spacers 75 prevent the rod 73 fromcontacting the tube 74.

When the sensor 70 is bent during a crash, the rod 73, which is made ofan electrically conductive material and thus electrically conducting,approaches and potentially contacts the tube 74, which is also made ofan electrically conductive material and thus electrically conducting. Inaddition to using the fact that when the rod 73 contacts the tube 74, anaccident of sufficient severity as to require airbag deployment hasoccurred, there are other methods of using the rod-in-tube constructionto sense crashes. One approach, for example, is to use appropriatecircuitry to induce an electromagnetic wave in the tube 74 relative tothe rod 73 with a wavelength what is approximately equivalent to thelength of the tube 74. The wave reflects off of the end of the tube 74,which is connected to the rod 73 though an impedance device, typically aresistor.

If the impedance between the tube 74 and rod 73 changes along its lengthsuch as would happen if the tube 74 were bent or crushed, a reflectionfrom the lower impedance point also occurs and by comparing the phasewith the wave reflected off of the end of the tube 74, the location ofthe lower impedance point can be determined. By comparing the magnitudesof the intermediate reflected waves over time, the rate of change in theimpedance can be determined and an estimate of the crush velocityobtained. Alternately, the time that the initial intermediate reflectionfirst occurred can be noted and the time when the tube 74 contacts therod 73 can also be noted and the difference divided into the deflectionrequired to cause rod-to-tube contact at that particular locationproviding a measure of the crush velocity.

If this crush velocity is above the threshold for airbag deployment asdetermined by a processor (not shown) which is coupled to theheader/connector 72 (and in a circuit with the rod 73 and tube 74), theairbag coupled to the processor can be deployed. If the sensor 70 ismounted far forward in the crush zone, then it will provide an earlymeasurement of the crash velocity providing an earlier deploymentdecision than prior art velocity change sensors that are located on thecrush zone boundary.

The shape of the sensor 70 shown in FIG. 5 or its rod-in-tubeconstruction is not limiting and is shown for illustration purposesonly. For the same vehicle shown in FIG. 7, other shapes of sensors maybe used and for a vehicle with a different front end, the sensor maytake any form sufficient to enable it to perform the desired functions,as described herein.

The rod 73 is maintained in a central location within the tube 74 asillustrated in FIG. 6 by means of the substantially cylindrical spacers75 that are placed at each of the bends 96 in the tube 74 and, in onepreferred embodiment, in the center of the lower horizontal portion 86as shown in FIG. 6. The spacers 75 are made from an electricallynon-conductive material, such as plastic or other suitable flexiblematerial such as rubber, thus preventing the completion of the electriccircuit through the spacers 75.

Although in the preferred embodiment shown in FIG. 5, spacers 75 areonly placed in the bends 96 and at the center of the horizontal portion86, in other embodiments, spacers 75 can be placed arbitrarily along thelength of the sensor 70 in order to adjust the sensitivity of the sensor70 to particular crash events. The effect of the spacers 75 is dramatic.The deflection required to cause electrical contact in the sensor at thecenter of the lower horizontal portion 86 is approximately 0.1 inches ifthe spacer 75 is not present, and greater than 1 inch if the spacer 75is present.

Also, the tubular form of the sensor 70 is only a preferred embodiment,and it may have other cross-sectional forms, e.g., rectangular, oval orpolygonal, depending on the particular need while the spacers 75similarly are constructed to substantially conform to the interior shapeof the sensor 70. The variable positioning of the spacers 75 providesthe advantage of the selective sensitivity of the sensor 70 to crashesin specific areas along the length of the sensor 70. As shown, thespacers 75 extend circumferentially about the rod 73 only at discretelocations in the tube 74 so that entire circumferential portions of therod 73 are spaced from the tube 74. When a coaxial cable is used asdescribed below, spacers are not required as the entire space betweenthe center and outer conductors is filled with dielectric material.

Although spacers 75 are shown to prevent electrical engagement of therod 73 and the tube 74, other spacing mechanism may also be provided toachieve the same function.

The crush velocity sensor of this invention is shown mounted on avehicle in FIG. 7 where a substantial portion of the vehicle has beenremoved to better illustrate how the sensor 70 is mounted. In theconfiguration in FIG. 7, the rearward portion 89 of the sensor 70 hasbeen eliminated and the sensor 70 extends only toward the outside of thevehicle. The vehicle structure shown consists of an upper radiatorsupport 81, two vertical radiator supports 82 and a lower radiatorsupport 83. The two vertical radiator supports 82 and the lower radiatorsupport 83 are attached to rails 90 which are the structures of thevehicle that support the front end.

A bumper structure 80 (of a particular vehicle) but not the bumperplastic cover is also illustrated in FIG. 7. The crush velocity sensor70 in accordance with the invention is attached to the upper radiatorsupport 81 by attachment structure, e.g., conventional hardware 76 and77, and to the lower radiator support 83 by attachment structure, e.g.,conventional hardware 78 and 79. Hardware elements 76, 77, 78, 79 areclamps having two holes for enabling a screw or nail to connect theclamps to the radiator supports. Obviously, any attachment structure issuitable for these purposes. Note that this arrangement is thefurthermost to the rear of the vehicle that such a frontal impact sensorcan be located. Generally, it will be located more forward in the crushzone.

During a frontal impact with either a barrier or another vehicle, forexample, bumper structure 80 is displaced toward the rear of the vehiclerelative to the radiator supports 81, 82, 83 of the vehicle to aposition where it impacts the vertical portions 84 and 85 of the crushsensor 70, which are mounted so as to be spaced away by attachments76-79 and thereby not in contact with the vehicle. This sequence isillustrated in FIGS. 7A and 7B which are views taken along lines 7A-7Aof FIG. 7. Upon impact with sensor vertical portion 85, bumper structure80 causes the rod and tube assembly of sensor 70, and at least verticalportions 84, 85, to bend which in turn causes the rod 73 to moverelatively closer to the inside of the tube 74, at locations 91, 92, 93,and 94, which can be measured by the change in impedance as is known tothose skilled in the art. This is known as time domain reflectometry.

By measuring this change in impedance over time, an estimate of thecrash velocity can be made. Alternately, by timing the interval from thefirst change in impedance until contact between the rod 73 and tube 74,the velocity can be determined and if above a threshold, the airbag canbe deployed. Although in this case four contacts are made between therod 73 and the tube 74, they will not occur simultaneously and thus thecrush velocity can be determined based on the first occurrence. In thismanner, any crash that causes the bumper structure 80 to be displacedtoward the rear of the vehicle will permit the crash velocity to bedetermined.

A key advantage of the sensor in accordance with this invention is thatit operates on bending. During a crash, the impact to a particular pointin or on the vehicle cannot be guaranteed but the fact that a lineacross the front, side or rear of the vehicle will not remain straightcan almost assuredly be guaranteed. Therefore, a sensor that is long andnarrow and responds to bending will be highly reliable in permitting thecrash velocity to be determined even in the most unusual crashes.

The sensor 70 in accordance with the invention can be designed to covera significant distance across the vehicle as well as along both sidesback almost to the B-pillar that increases the probability that it willbe struck by crushed material and bent as the crush zone propagates inthe vehicle during a crash. At the same time, the sensor 70 can be smallso that it can be located in a position to sense the fact that one partof the vehicle has moved relative to some other part or that thestructure on which the sensor 70 is mounted has deformed. In thisregard, sensor 70 may be positioned at the rear of the crush zone of thevehicle but for reflectometry measurements it is most appropriatelypositioned as far forward in the vehicle as practical.

The particular implementation of the rod-in-tube is for illustrationpurposes only and many other technologies exist that permit the velocitychange of a portion of an elongate sensor due to a crash to bedetermined and thereby the local velocity change of a part of a vehicle.Such alternate technologies include the use of distributed piezoelectricmaterials to measure local crush, and distributed accelerometers thatare attached by rigid structures or arms that transfer the accelerationto accelerometers.

Not all crashes involve the bumper and in a survey of crashed vehicles(see SAE Paper No. 930650 (8)), as many as about 30% of the surveyedvehicles were involved in crashes where the bumper was not primarilyinvolved. A typical crash of this type involves a vehicle that isbraking and therefore pitching forward which lowers the front bumper andraises the rear bumper. If this first vehicle is struck in the rear byanother, second vehicle which is similarly pitching, the second strikingvehicle can impact the first struck vehicle with the front bumper of thesecond striking vehicle riding underneath the rear bumper of the firststruck vehicle. In this case, the bumper of the first struck vehiclewill impact the grill and radiator of the second striking vehicle anddisplace the vertical portions 84 and 85 of the crush switch sensor inaccordance with this invention. As such, the crash velocity can bedetermined and the airbag deployed. The under-ride problem is compoundedby the recent increase in the number of SUVs and pickup trucks whichtend to have higher bumpers.

When the bumper structure 80 is involved in an accident, it generallymaintains its structural shape until it begins impacting the radiatorand other vehicular structures behind the radiator. This is after it hasimpacted the sensor 70. Since the bumper structure 80 has not yetdeformed when it strikes the sensor 70, the sensor 70 senses the crushof the vehicle equivalent to the distance between the rear of the bumperstructure 80 and the sensor 70, plus the amount of sensor deflectionrequired to deform the sensor 70 and change its properties such as itsimpedance.

If the bumper structure 80 is not primarily involved in the accident,the amount of penetration into the vehicle required to activate thesensor 70, measured from the front of the bumper structure 80, will begreater by the amount of the thickness of the bumper structure 80. Inthis manner, the sensor system requires greater penetration into thevehicle in bumper underride crashes. This results in a longer sensingtime which is desired when the sensor 70 is acting as a switch sincesuch crashes are softer than those crashes which involve the bumper andtherefore there is more time available before deployment of the airbagis required. On the other hand, for crash velocity sensors, it isdesirable that the sensor be as far forward as practical since thesensor functions by measuring the velocity of the crash and not thecrush. Sensor 70 can be designed to act in both capacities, as avelocity measuring device and as a crush measuring device, at theexpense of somewhat later triggering.

In some cases, it is necessary to further desensitize the sensor tobumper underride type crashes to make the sensor less sensitive to deerimpacts, for example. Every year in the U.S. there are more than 300,000impacts with deer and in most cases, airbag deployment is not needed.Some currently used sensor systems, however, can cause the airbag todeploy on deer impacts. When impacted at high speeds, the crash pulse inthe non-crush zone can be similar to the crash pulse from a barriercrash up to the time that the decision must be made to deploy theairbag. In such cases, electronic sensors operating on the non-crushzone crash pulse will determine that the airbag deployment is required.Currently used crush zone sensors may be mounted above the bumper andproject outward from brackets attached to the upper radiator support.These sensors are impacted by a deer even at lower speeds and experiencea velocity change sufficient to cause deployment of the airbag.

Crush velocity sensors in accordance with this invention, however, canbe desensitized in a manner such as shown in FIG. 8 so as to render itinsensitive to deer impacts (or impacts with other large animals). Inthis case, a section designated at 95, of at least the vertical portion84 of the sensor 70, has been displaced rearward to render it lesssensitive to deer impacts. Section 95 is substantially U-shaped.Vertical portion 84 and horizontal portion 86 can also be constructedwith a rearwardly displaced portion to thereby enable adjustment of thedegree of sensitivity of the sensor 70.

Approximately 2% of frontal crashes involve impacts to the vehicle belowthe bumper. In a typical case, a vehicle impacts with a large stone,tree stump or short or low pole that miss the bumper. This type ofaccident is expected to become more common since in order to makevehicles more aerodynamic, vehicle hoods have been made lower and theradiators have also been lowered until as much as one-third of theradiator now projects below the lower edge of the bumper. An impact witha short pole or curb 97 such as shown in FIG. 9 where the pole 97interacts with the lower portion of the radiator, can result in anairbag-required crash which will not be properly sensed by some sensortechnologies, e.g., ball-in-tube based crush zone sensors. These crushzone sensors are typically mounted above the bumper and therefore wouldnot be in the crush zone for this kind of a crash causing them totrigger on the non-crush zone crash pulse resulting in a late deploymentof theairbag.

The preferred embodiment of the crush switch sensor of this inventionshown in FIG. 9, on the other hand, stretches across the front of thevehicle and will trigger thereby causing the airbag to deploy in timefor these crashes.

About the most common of all real-world airbag crashes involve impactswith poles. Pole impacts are some of the most difficult crashes to senseproperly with current airbag sensor technology. Poles that can requireairbag deployment vary in diameter from as little as about 4 inches togreater than about 24 inches. They involve such objects as fence posts,light poles, trees and telephone poles that are the most commonobstacles found along the sides of roads. An impact into a pole at anyposition along the front of the vehicle can result in a serious accidentrequiring deployment of the airbag. The stiffness of the vehicle,however, varies significantly from one part of the front to the other.For most vehicles, the center front is the softest part of the vehicle,and the rails are the stiffest. In a typical accident, the bumper willbuckle around a pole resulting in a soft crash pulse until the polepenetrates sufficiently into the vehicle that it begins to engage majorstructural members or the engine at which time, the pulse becomes verystiff. This type of crash pulse is particularly difficult for non-crushzone sensors to sense properly.

Pole crashes are typically staged by automobile manufacturers duringtheir airbag development programs, but they are limited in scope. Theytypically involve large poles that are one foot or more in diameter andare usually run at high speeds. It has been found, however, that thinpoles at low speeds are much more difficult to enable proper sensing forairbag deployment than thick poles at high speeds. They are also muchmore common in the real world. Non-crush zone sensors have aparticularly difficult time in sensing pole crashes especially thoseinvolving thin poles at low velocities, since the crash pulse is verysoft until it is too late to initiate airbag deployment. Conventionalcrush zone sensors, such as the ball-in-tube sensors, function properlyas long as the sensor is located in-line with the impact point of thepole. When this is not the case, and especially when the impact speed islow, these sensors can fail.

A particular case, for example, involved a vehicle that has threeball-in-tube sensors mounted in the crush zone, one center-mounted andone on each side approximately in line with the rails. This vehicleimpacted a pole at approximately 15 miles per hour at a point midwaybetween the front center and side sensors. An examination of the vehicleshowed that there was no crush at either of the sensor locations. Inthis case, the sensors triggered the airbag late based on the non-crushzone crash pulse as described in U.S. Pat. No. 4,900,880. Before theairbag deployed, the occupant had already impacted with the steeringwheel and although conscious after the accident, later died frominternal injuries.

The crush velocity disclosed here, in the embodiment illustrated in FIG.7, would have measured the crash velocity and caused the airbag todeploy in time for this and all other pole impacts since it stretchessubstantially across the entire front of the vehicle, i.e., from oneside of the vehicle to the opposite side of the vehicle. Of course, thesensor 70 may be designed to stretch across only a portion of the frontof the vehicle in which case, it would be beneficial but not required touse multiple sensors. The sensor 70 could also be designed to stretchacross a portion of or all of the rear of the vehicle or along a portionof or the entire side of the vehicle (as discussed below).

In a small but significant percentage of automobile crashes (less thanabout 2%), the point of impact is outside of the main vehicle supportingstructure, that is typically the rails. In a common accident, a vehicleimpacts a pole at approximately the location of the headlights at aslight angle and the pole penetrates into the vehicle with littleresistance until it encounters the front wheel structure at which pointthe vehicle rapidly stops. This crash cannot be properly sensed by most,if not all, conventional airbag sensor system in use today. Electronicnon-crush zone mounted sensors will either trigger late or not at alldue to the very soft nature of this crash up to the point where the poleimpacts the wheel structure, which is too late.

Since conventional crush zone sensors are usually mounted inside of therail structure, they are not in the crush zone for this crash, which isusually exterior of the rail structure. They also, therefore, wouldeither not trigger or trigger late. The crush sensor as shown FIG. 7projects only slightly beyond the rail structure and therefore couldalso miss this type of crash. The extension of the upper horizontalportions 87 and 88, however, will permit the crush sensing sensor tosense this type of crash. These extensions would trigger the deploymentof the airbag in this pole crash and other airbag desired crashesoutside of the rail structure. This crash is a soft crash and thereforethere will be substantial penetration before the sensor must trigger.The upper horizontal portions 87 and 88 therefore could be angled towardthe rear in the vehicle to adjust the penetration required for thesensor to trigger. Alternately, the crush velocity sensor of thisembodiment of the invention can extend along the entire side on thevehicle almost to the B-pillar and thus can sense this crash. A crushswitch sensor, on the other hand, would be too sensitive if placedadjacent the side of the vehicle. By measuring the crash velocity, as isdone in the sensor of this embodiment of the invention, his is not aproblem and the sensor can be placed as close as practical to theexterior surfaces of the vehicle.

In order for current technology crush zone sensors to sense crashesoutside of the rails in time, additional sensors would have to be placedoutboard of the rails. As mentioned above, even three sensors areinsufficient to catch all pole crashes to the front of the vehicle, suchas the low pole crash described above, and when bumper override crashesare considered, additional sensors are required. A primary advantage ofthe crush or crush velocity sensors of these embodiments of theinvention is that a single sensor can be used to sense crashes to allportions of the front and most portions of the sides of the vehicle. Toachieve the equivalent coverage using conventional sensors would requireat least five and probably more sensors. The manufacturing cost of asensor described in this embodiment of the invention is about equivalentto the manufacturing cost of a single ball-in-tube crush zone sensor.Therefore, in addition to the substantial performance advantage, thereis also a substantial cost advantage in using the sensor describedherein.

In addition, a significant cost in a sensor system is the cost of thewires to connect each sensor to the remainder of the airbag system. Itis typical for a wire and connector assembly plus the cost of insulationto be as much as half of the cost of the sensor itself. In sensorsdescribed herein, a single wire assembly is all that is required toconnect the sensor to the airbag system. It would also be possible towirelessly connect the sensor assembly to the airbag system. Withconventional crush zone sensors, a separate wire assembly is needed foreach sensor. Finally, in order to minimize the possibility of theconventional crush zone sensor from rotating during angle crashes, forexample, the mounting structure, typically the upper radiator support,is frequently strengthened to provide a more rigid mounting structurefor the sensor. This modification to the vehicle structure is notrequired for sensors described herein and therefore additional costsavings result. To be able to measure the velocity change of the crash,additional electronics are required that will increase the cost of thesensor of this embodiment of the invention compared to a pure crushswitch crash sensor.

As discussed above, and in several of the cited references on sensingside impacts, crush sensing alone is not the best technical solution forsensing side impacts. In spite of this fact, Volvo has marketed a sideimpact airbag protection system where the sensor is a crush sensingsensor, although it is a point sensor and not a rod-in-tube geometry. Inthe event that other automobile manufacturers choose this approach, therod-in-tube crush sensor described herein can be used as shown in FIG.10 which is a side view of the sensor of this invention shown mounted ona vehicle to sense side impacts. One advantage of the rod-in-tube sensoris that it can cover a large area of potential crash sites at littleadditional cost. Thus, a single sensor can stretch along the entire doorin whatever shape desired, e.g., linearly as shown at 98 in a positionsubstantially parallel to the door panel. Thus, the sensor 98 wouldmeasure the crush velocity upon impact at any location along the door.This solves a potential problem with the Volvo system that requires thatthe crash take place at a particular location for the airbag to bedeployed.

In addition, sensors could extend across the side panels of the vehicleand not only across the doors. Such a sensor can also be used for rearimpacts.

The use of a rod-in-tube sensor for side impacts as well as one forfrontal impacts is particularly attractive since it can be easilyattached to the same diagnostic module. Thus, the same Diagnostic andEnergy Reserve Module (DERM) can be used for frontal, side and even rearimpacts. A particularly economical system results if these sensors areused for the entire vehicle permitting a simple electronic diagnosticsystem to be used, in contrast to the complicated microprocessor-basedsystems now in use. Thus, superior protection for the entire vehicle forcrashes from any direction can be obtained at a substantial costreduction over currently used electronic systems.

Some of the objections for use of a crush sensing sensor for side impactare overcome by the use of the sensor to measure the crash velocityrather than pure crush. A pure crush sensor is prone to inadvertenttriggering since the amount of crush in side impacts cannot be used as ameasure of impact velocity due to the short triggering time requirement.Use of the sensor of this embodiment of the invention in conjunctionwith an electronic sensor for side impacts will be discussed in detailbelow.

The application of the sensor of this embodiment of the invention forrear impacts is in theory and practice similar to that for frontalimpacts. In contrast to frontal impacts, there is not yet universalagreement as to the velocity change at which the deployment of aheadrest-mounted airbag is needed. Many whiplash injuries occur at verylow velocity changes, as low as about 5 mph. The replacement cost forsuch an airbag will be substantially less than for frontal impactairbags, consequently the deployment velocity could be made lower. Onthe other hand, if the headrest is properly positioned, only highvelocity impacts would require airbag deployment. It is important tokeep in mind that whiplash injuries are the most expensive group ofautomobile injuries even though they are usually not life-threatening.Any airbag in the headrest can cause more injury than help due to theproximity of the occupant's head to the headrest.

Thus, it is conceivable that the threshold velocity can be determined asa function of the position of the headrest. The position of the headrestmay be determined by a sensor system and then a processor coupled to thesensor system and to the rear impact sensor would factor in the positionof the headrest when determining an appropriate threshold velocity abovewhich the airbag should be deployed.

The choice of the marginal deployment velocity significantly impacts thelocation of the rod-in-tube crush switch sensor but has much less effecton the crush velocity sensor of this invention. Also, the rear endsections of automobiles differ substantially in their structure,stiffness, and suitable sensor mounting locations. In some vehicles, theoptimal sensor mounting location will be in the trunk lid. In others,especially if low velocity impacts are to be sensed, a location behindthe bumper is appropriate. In many vehicles, the proper location for acrush switch sensor is in the middle of the trunk volume, an impracticalplace to mount any sensor. For the crush velocity sensor of thisembodiment of the invention, on the other hand, this is not a problemand the sensor can be mounted at a more convenient rearward location.

Due to this wide variability in sensor strategies and resulting sensorlocations and geometries, FIG. 11 illustrates a general sensor 99arbitrarily mounted to the rear of the vehicle to sense rear impacts,and as shown, in a position extending across substantially the entirewidth of the rear of the vehicle. Portions of the vehicle are removed topermit viewing of the sensor 99. The determination of the propermounting position and sensor design follows the same strategyillustrated above and in the cited references. Other sensor designs suchas the ball-in-tube or spring mass sensors such as the rolemite can beused for sensing rear impacts and the sensing or rear impacts is notlimited to the particular designs disclosed herein.

The environment experienced by a sensor mounted in the front of theradiator on a vehicle is one of the most severe in the automobile. Inaddition to the extremes of temperature encountered between winter inAlaska and summer in the Arizona desert, this location is impacted byhail, stones, dust, dirt, salt water, radiator coolant, steam cleanerand occasionally even battery acid. This sensor must be capable ofsurviving any combination of these environments for the useful life ofthe car that is typically considered to be in excess of ten years. It isimportant, therefore, that this sensor be hermetically sealed. A greatdeal of effort has been put into the ball-in-tube crush zone sensors toseal them from these environmental influences. Nevertheless, sensorsthat have been on vehicles have been dissembled and found to containmoisture. Although moisture would not have as detrimental effect to therod-in-tube sensor described here as it does to ball-in-tube sensors,the sensor has nevertheless been designed to be truly hermeticallysealed as described below.

FIG. 12 is a cross sectional view of the header/connector assembly 72shown mounted on the tube 74 and rod 73. One of the spacers 75 is usedto position the rod 73 inside the tube 74 as described above. Theprimary seal for this sensor 70 is injected and cured in place and isurethane or a silicone rubber compound 100.

Current ball-in-tube crush zone sensors are attached to the vehicle wireharness and, thus to the remainder of the airbag system, by means of apigtail which is a wire assembly emanating from the sensor at one endand having a connector at the other end. It is believed that theenvironment in front of the radiator is too severe for connectors,therefore connectors integral with the sensor have not been considered.This pigtail is one of the most expensive parts of the standardball-in-tube crush zone sensor. Substantial cost savings result if theconnector could be made integral with the sensor. This has beenaccomplished in the crush switch sensor of the current design as shownin FIGS. 5, 7 and 12.

The sealing technique used for the header/connector is to form a rubbermold within the housing and to pump a rubbery material such as urethaneor silicone rubber, or similar compound, 100 into the cavity. This isaccomplished in such a manner that the air is displaced and forced toflow through various clearances between the parts in much the samemanner as air is forced out of a plastic injection mold when the liquidplastic is forced in under pressure. The rubber compound 100 is injectedthrough hole 101 in the bottom of the connector portion of the assemblyand flows upward as the air flows out through holes or slots 111 in tube74 and finally out of the assembly through the clearance between thetube 74 and a plastic dam 110. The plastic dam 110 is a part that fitssnugly to the tube 74 and also against a plastic header body 113 of theheader/connector assembly 72. These snug fits permit the air to flowwhile offering a substantial resistance to the flow of the rubber 100.In this manner and through the proper geometric shaping of the variousparts, all but a few minute air bubbles are effectively removed and therubber 100 thereby attaches and seals to all of the relevant surfaces.

A second dam 109 is also used to limit the passage of the rubber intothe main body of the sensor 70. The spacers 75 typically contain agroove to permit the passage of grease, as will be explained below, andthe dam 109 effectively seals this area and prevents passage of therubber. Since the grease is typically pumped into the sensor 70 afterthe header/connector assembly 72 is assembled, this last spacer 75adjacent to the header/connector assembly 72 need not have the grooveand thus the dam 109 and spacer 75 can be made as one part if desired.

The seal is thus made by the steps of:

a) assembling the header/connector assembly 72 to the rod-in-tubeassembly 73/74 creating at least one enclosed cavity therein having atleast one inlet port 101 for injecting a rubber compound and at leastone narrow passage for air to escape (the clearance between tube 74 anddam 110), this passage being sufficiently narrow as to permit only asmall amount of rubber compound to flow out of the assembly during thefilling process, but large enough to permit air to easily flow out ofthe assembly;

b) injecting an uncured rubber compound through the inlet port(s) insuch a manner that the at least one narrow passage remains open duringthe injection process until the cavity is substantially filledpermitting air within the cavity to be displaced by the rubber compound;and

c) curing the rubber compound.

Usually a room-temperature curing rubber compound is used and thus thecuring process comprises storing the assembly until the curing iscomplete. In many cases, the temperature of the assembly is elevated toaccelerate the curing process and in others, the rubber is exposed toultra violet light to affect the cure.

Tests were run on this system whereby the assembly was held at about −40degrees Celsius for more than twelve hours and then immersed intoboiling water and then into near freezing water containing a penetratingdie. After tens of cycles, the test units were cut open to search forthe penetration of the die that would indicate a failure of the seal.None was found. In contrast, a commercially available ball-in-tubesensor failed on the first cycle. This test is more severe than anysensor is likely to experience in the field and therefore proves theviability of the sealing system.

A preferred plastic material used for the header/connector is 30%glass-filled polyester although other plastic materials would work aswell. Standard crush zone sensor connectors are frequently made fromunfilled NYLON® and this would also be suitable for the header/connectordesign used in the sensor of this invention. Although unfilled NYLON®has a high coefficient of thermal expansion, the urethane or siliconerubber has even a higher one and therefore the seals between the NYLON®and metal parts will remain intact.

The lower portion of the header body 310 of header/connector assembly 72shown in FIG. 12, is in the form of a mating connector which attaches tothe wire harness connector provided by the automobile manufacturer.Connector pins 104 and 105 are extensions of the header pins 102 and103, which are connected to the rod 73 and tube 74, respectively, andare designed to mate with the appropriate connector, not shown indetail. Connector pins 104 and 105 are made of an electricallyconductive material. Upon completion of the circuit via contact betweenthe rod 73 and the tube 74 upon a crash, current flows through theconnector pins 104, 105, header pins 102, 103 and rod 73 and tube 74.The header pins 102, 103 are formed from, e.g., sheet brass, in such amanner that they surround the rod 73 and tube 74 and are electricallyconnected thereto. This is accomplished in the case of the tube 74, forexample, by solder-coating the end 112 of the tube 74. A mating portion107 of the header pin 103 fits snugly inside the tube 74 and, throughinducton heating, is soldered to the tube 74. Similarly, mating portion106 of header pin 102 surrounds the rod 73 that has been soldered-coatedat its end 108.

The header pins 102 and 103 are first formed from, e.g., tin-platedbrass material, into the proper shape and then placed in a mold in aninsert molding operation to form the header/connector assembly 72. Notethat a reflection will come from the different impedance in theconnector but it will be at a known position and can be ignored. This isbelieved to be a ground-breaking use of an integral connector for acrush zone mounted sensor.

Spacers 75, in addition to their use in a straight portion of the rodand tube assembly as shown in FIG. 6, are also placed in each of thebends 96. A partial cutaway view of a typical bend 96 is shown in FIG.13. During assembly the spacers 75 are placed on the rod 73 and the rod73 is inserted into a straight tube 74 with the spacers 75 located ateach position where the tube 74 will be bent. The tube 74 is then bentat spacer locations using conventional tubing benders and the rod 73 isalso forced to bend by virtue of the spacer 75. The spacers 75 areformed from extruded plastic tubing and are slightly smaller in diameterthan the tube 74. The internal diameter of the spacer 75, however, issuch as to require a press fit onto the rod 73. Thus, the spacers 75 areheld firmly on the rod 73 as the rod 73 is inserted into the tube 74.Spacers 75 used in the bends are typically about 3 inches long when usedwith a 0.5 inch tube and a 1.0 inch bend radius. Typically asubstantially thinner tube is used sometimes as small as ⅛ inch indiameter.

In a typical large tube assembly, the tube outside diameter isapproximately 0.5 inch and the wall thickness approximately 0.035 inchesand in a small tube assembly, the outside diameter is approximately 0.25inches and the wall thickness is about 0.02 inches. The large tubedesign is used when there is no convenient structure to mount the sensoragainst and it is vulnerable to abuse, while the thin or small tubedesign is used when it can be mounted nearly flush against the radiatorsupport, for example, or in a protected location such as inside of thevehicle door.

The end 71 of the sensor 70, which does not have the header/connector72, is welded closed as shown in FIG. 14. An impedance such as aresistor 117 is placed across the contacts in the sensor 70 to createthe reflection at the end on the sensor 70. This is accomplished asshown in FIG. 14 by attaching a resistor 117 to an end 114 of rod 73 andto an end 115 of the tube 74. The end 115 is formed by squeezing thetube 74 in the appropriate set of dies which gradually taper and flattenthe tube 74, squeezing the end of resistor 117 and closing off the tube74 with a straight line seal. The end of this seal, 116, is then TIGwelded using conventional equipment to assure a hermetic seal.

FIG. 15 is a view of the sensor of FIG. 5, with half of the tube 74 androd 73 removed but showing complete spacers 75, taken along lines 12-12and showing the location of all of the spacers 75 and the rod 73 andtube 74.

A typical length of the span between spacers 75 for the verticalportions 84 and 85 of FIG. 5 is approximately 10-15 inches. In thisconfiguration, the rod 73 will actually deflect and contact the tube 74during minor accidents and therefore in a preferred embodiment of thedesign, the tube 74 is filled with a damping material which is typicallya viscous liquid or grease which has been formulated to operate over therequired temperature range of from about −40° C. to about 125° C. Thisgrease should have approximately the same dielectric constant as theplastic spacers 75 to minimize extraneous echoes. For the purposes ofthis disclosure, the term grease will be used to include all flowablematerials having a viscosity between about 100 and about 100 millioncentipoises. This would include, therefore, all silicone and petroleumand other natural and synthetic oils and greases in this viscosityrange.

This grease 118 is shown in FIG. 16 where half of the tube 74 has beenremoved to show the grease 118 filling substantially the entire tube 74.Small voids 119 are intentionally placed in the grease 118 to allow fordifferential expansion between the grease 118 and the tube 74 due tovariations in temperature. When grease 118 is used, small channels, notshown, are provided in the spacers 75 to permit the grease to flow pastthe spacers 75 as the sensor 70 is pumped full of the grease 118.

The sensor described and illustrated above is designed to catch allimpacts to the vehicle regardless of where they occur providing thesensors are properly located. For frontal and rear impacts, the severityof the crash required to cause sensor triggering is determined by theamount of crush of the vehicle at each location which is necessary tocause the sensor to experience a measurable and timely velocity change.The amount of crush necessary to transmit this velocity change torelative motion of the rod in the tube at any location can be variedarbitrarily by the distance the sensor is located from the front or rearof the vehicle, by the location and characteristics of spacers in thesensor and/or by the location and characteristics of the supports thatare used, as discussed above.

Steel has been used for the materials for the rod 73 and tube 74 for apreferred embodiment described herein. The tube 74 is in an annealedstate to promote easy forming to the required shape and to promotedeformation during the crash. The rod 73, on the other hand, istypically hardened so as to maintain its spring temper and promote goodpositioning with the tube 74 when the assembly is bent. The outside ofthe sensor 70 is coated with a protective coating to prevent it fromrusting during the estimated 10 year life of the vehicle. The interiorsurfaces are coated with grease to prevent corrosion in those caseswhere the entire sensor in not filled with grease. Other materials suchas aluminum, brass or even plastic with an electrically conductivesurface coating could be used for the rod and tube.

The rod and tube described above, for the large tube design, have beendesigned to require approximately fifty to one hundred pounds of forcein order to cause the sensor to significantly bend. This is to minimizethe chance of inadvertent deployment during routine vehicle maintenance.For cases where the sensor is in a protected location, the small tubedesign typically uses about a 0.25 inch diameter tube with about a0.0625 inch diameter rod.

Once the crush velocity sensor of the present design bends significantlyto where the rod 73 contacts the tube 74, it remains latched in theconductive state for the duration of the crash. This important featureguarantees overlap between the triggering of the crush zone sensor andthe passenger compartment-mounted arming sensor when used for frontaland rear impacts.

The sensor described and illustrated herein can use an impedance such asa resistor. In contrast to many sensor designs, monitoring of the entirefunctioning of the sensor continuously occurs with the crush velocitysensor of this invention. The driving and control electronics cancontinuously transmit waves into the sensor and monitor the reflectionsthat are returned. Thus, if there is a broken connection for example,the system will not get the expected return and can signal to the airbagsystem to display a fault.

The tube of the sensor described herein can be electrically grounded tothe vehicle. In some applications, it may be desirable not to ground theoutside of the tube in which case, the tube might be surrounded by aninsulating plastic tube. The use of a grounded outer tube has theadvantage of providing shielding from electro-magnetic radiation for therod and thus minimizing the chance of an inadvertent signal reaching theelectronic sensor, for example, as the vehicle passes through strongelectro-magnetic fields.

A primary advantage of the sensor described herein is its coaxial designthat permits arbitrarily shaping of the sensor to adapt the sensor to aparticular vehicle and to a particular place on that vehicle. There are,of course, other designs that could also be arbitrarily shapedincluding, but not limited to, tubes having a square, elliptical ortriangular cross-section. All of these and similar geometries areconsidered tubes for the purpose of this invention. Similarly, the rodcan take on a variety of shapes without departing from the teachings ofthis invention. In particular, the rod can also be a tube which hasadvantages in minimizing the effects of vibration. The rod need not beround and can be triangular, elliptical, square or even ribbon-shaped.All of these geometries are considered rods for the purposes of thisinvention.

Another key feature of this invention is that, when the sensor isproperly mounted on the vehicle, plastic deformation of the tubegenerally occurs prior to triggering of the sensor and always occurs ina crash where the deployment of the airbag is required. This results inthe sensor latching closed during the crash but it also prevents it frombeing reused on the same or another vehicle. In an alternateconfiguration, the dimensions of the rod and tube and the materialproperties are chosen so that the sensor can be caused to trigger withsufficient force without causing plastic deformation. This usuallypermits a more accurate estimation of the crash velocity.

The use of grease to dampen the motion of one or more of the parts of acrash sensor has been disclosed herein. Other crash sensor designs, andparticularly crush switch sensor designs, could also make use of agrease to surround and dampen the motion of one or more of the internalparts of the sensor.

The hermetic sealing system disclosed herein has permitted use of anintegral header/connector thus eliminating the need for the pigtail andsubstantially reducing the cost of airbag sensors for frontal mountingin the “splash zone”. Now that this system has been disclosed, otherapplications of this system to other types of crash sensors will becomeobvious to those skilled in the art.

In another implementation, the crash velocity can be determined throughthe use of two crush switch crash sensors. If two sensors of the typedisclosed above are mounted on a vehicle with one closer to the frontthan the other, then, during a crash, the forwardmost sensor willtrigger first followed by the second, more rearward sensor. If thespacing between the sensors is known, an estimate of the crash velocitycan be obtained by measuring the time between switch closures. In thismanner, the use of two switches can be used to determine the crashvelocity.

This concept can be further improved if the phase measurement system ofthis invention is added. In this case, therefore, the location of thecontact will be determined in each crush switch and then the velocitydetermined as discussed above. This is another method of obtaining boththe velocity change and the location of the impact and is perhaps moreaccurate that the single sensor system. This concept can be appliedusing other technologies where the impact with a sensor can bedetermined. If the sensor contains distributed piezoelectric material,for example, an impact will send a voltage spike to the evaluationcircuitry.

For cases where actuation by bending of the sensor is not required andthe sensor can be configured to reliably be impacted during the crash, acoaxial cable design is appropriate. In this case, a cable is selectedwhich will deform under a 10 to 500 pound load in a manner such that theimpedance change that occurs during the deformation can be measured.Since in most cases, the resisting deformation force is small comparedwith the crush forces of an accident, an appropriately mounted cableshould provide an accurate measurement of the crash velocity. Such asensor can be configured such that a single sensor will sense crashesfrom near the B-pillar on the driver side, across the entire front ofthe vehicle to near the B-pillar on the passenger side as shown as 121in FIG. 17. The sensor would thus have a substantially U-shaped portionand would extend substantially completely across the front doors betweenlongitudinal edges of the doors.

In one embodiment, an electronic control module 122 including aprocessor is mounted in the passenger door and feeds electromagneticwaves, generated by an electromagnetic wave generator, having awavelength on the same order as the length of the coaxial cable intocable 121. A similar sensor can also be used for the rear doors as shownat 120, and would thus extend substantially completely across the reardoors between longitudinal edges of the doors. This device acts like atime domain reflectometer. That is, the magnitude and location of anychanges in impedance are measured. A change in impedance can be relatedto the magnitude of the crush of the cable and thus by successivemeasurements of the change in impedance, the crush velocity can bedetermined by a processor, possibly embodied in the control module 122.In this case, the outside conductor of the coaxial cable is grounded andthe interior conductor acts as an antenna. The cable is terminated inthe driver door with an impedance-matching resistor to complete theassembly.

The use of a coaxial cable and time domain reflectometry was discussedabove. Another possible method is to use light and a fiber optic cable.In one implementation, Abacus Optical Mechanics of Oxnard, Calif., hasdemonstrated how a fiber optic cable as it is distorted can restrict thepassage of light and that this effect can be used to measureacceleration, pressure etc. If this device is fed with modulated light,then the location of the disturbance along the fiber can be determined.

Another embodiment of the invention uses parallel strips of conductivematerial and is sometimes referred to as a tape switch sensor and isdescribed in detail in the above-referenced patents and therefore willnot be repeated herein.

Knowledge of the location of the impact, e.g., as detected using thecoaxial cable sensor described above, can be used to enhance and improvethe effectiveness of an occupant restraint system. For example, if analgorithm is used to control the deployment and operation of occupantrestraint devices, the algorithm can be designed to consider thelocation of the impact, e.g., by factoring in the location of the impactwhen determining which airbags to deploy and the inflation of thoseairbags. In some crashes, it might be the case that only the sideairbags are deployed if the crash location is along the side of thevehicle. On the other hand, it might be the case that only the frontairbags are deployed if the crash location is in the front of thevehicle. Of course, both the front and side airbags could be deployed ifsuch deployment is warranted by the impact location.

In order to prevent seismic sensors, such as the ball-in-tube oraccelerometer-based sensors, from rotating in a crash, it has becomecommon to increase the strength of the radiator support or otherstructure on which the sensor is mounted. The sensor mounting bracket,however, must then permit the sensor to move relative to this structure,complicating the bracket design, or this structure must be weaklyattached to the remainder of the vehicle so that the whole assembly willmove in the crash. This added structural strength adds weight to thevehicle and is not needed for the sensors described herein. It is evendesirable for the sensors described herein to be mounted on weakerstructural members in order to enhance the chance for the structure todeform, especially in soft crashes. The use of the rod-in-tube, coaxialcable, tape switch or other elongate sensor disclosed herein, therefore,results in a weight saving for the vehicle that is very important withthe increasingly stringent fuel economy standards mandated by the U.S.Government.

Operation of the crush zone crash sensor of this invention, as well asall others, can be critically affected by the material which is locatedbetween the sensor and the front of the vehicle and the geometry of thismaterial as it crushes and comes back to strike the sensor. Sensors ofthe present invention are considerably more tolerant to variations inthe geometry of this material for two reasons. Considering thecompression mode, the length of the sensor can be increased so that theprobability of it being impacted is very high.

Alternately, in the bending mode, the sensor can be attached to twoportions of the vehicle that are likely to experience relative motionduring the crash. In this latter case, the two portions of the vehicleeffectively become extensions of the sensor. In some cases, the radiatorsupport structure is designed so that it will always deform at aparticular location with the result that the sensor can be quite shortsince the entire radiator structure becomes an extension of the sensor.In other cases, such a location is not readily available and the sensormust be made longer to guarantee that it will be bent or compressed in acrash by crushed material coming from areas further forward in thevehicle.

The use of crush initiators is becoming increasingly common in vehicledesign. These usually take the form of a hole, wrinkle, notch or bendintentionally placed in a structural member to cause the member to bendin a particular manner during a crash. As the sensor of the presentinvention is adapted to a particular vehicle, the use of crushinitiators to control the manner in which the member, on which thesensor is mounted, bends will result in a shorter and more reliablesensor. Additional, usually minor, design modifications can also be usedto permit the sensor to be mounted in protected locations so as tominimize the chance of sensor damage during vehicle maintenance.

The force required to cause sensor closure is an important designparameter of the sensor of this invention. In one typical designconfiguration, a 20 pound force on the sensor is required to move thefront contact strip toward the rear member sufficiently to permit avelocity to be measured. This force is sufficient so that it is unlikelyfor the sensor to inadvertently provide a velocity indication sufficientto cause airbag deployment during vehicle maintenance, stone and someanimal impacts and yet, this force is quite low compared to the forcestypically experienced during even marginal crashes.

The angle required to cause sensor closure is also an importantparameter of the sensor of this invention. In one typical designconfiguration, a 15 degree bend angle of the sensor is required to movethe front contact strip toward the rear member sufficiently to cause afalse velocity reading indicative of a crash in the bending mode. Thisangle is sufficient so that it is unlikely for the sensor toinadvertently close during vehicle maintenance, stone and some animalimpacts and yet, this angle is quite low compared to the relativedisplacements and the angles that will occur in a sensor mounted on twolocations which typically move relative to each other in even marginalcrashes.

Also disclosed above is a vehicle crush detecting device in combinationwith a vehicle which comprises a sensor assembly including a firstelongated electrical conductor, a second elongated electrical conductor,and a coupling mechanism for coupling the second electrical conductor tothe first electrical conductor so that the first and second electricalconductors are parallel and substantially coextensive to each other andthereby form the sensor assembly. The coupling mechanism insulates thesecond electrical conductor from the first electrical conductor. Anattachment mechanism attaches the sensor assembly to the vehicle atleast two spaced apart positions. In use, when a portion of the vehiclecrushes to contact the sensor assembly in the span between the at leasttwo spaced apart locations, the sensor assembly crushes at the contactlocation causing the first electrical conductor to approach the secondelectrical conductor and the impedance therebetween changes as describedabove. The coupling mechanism may comprise a header/connector assemblyat one end of the sensor assembly.

The first conductor may be a tube, which is preferably deformable, andthe second conductor may be a rod arranged in the tube. Insulatingdevices, e.g., round spacers, are positioned at least two points betweenthe first and second conductors for insulating the first conductor fromthe second conductor. The spacers extend only at discrete locationscircumferentially between the first and second conductors. The firstconductor may also be the outer conductor of a coax cable and the secondconductor may be the inner conductor. The sensor assembly may beattached to the vehicle in a front region of the vehicle so as to detectcrush velocity of the front region of the vehicle or at a rear of thevehicle so as to detect crush velocity of the rear of the vehicle. Also,the sensor assembly may be attached to the vehicle on a side of thevehicle so as to detect crush of the side of the vehicle. In this case,the sensor assembly can have an elongate portion attached in a positionsubstantially parallel to a door panel in a door on the side of thevehicle.

The header/connector assembly hermetically seals a space between thefirst and second conductors at one end thereof while the space betweenthe conductors at the opposite end is closed. The header/connectorassembly includes electrical connector pins electrically coupled to thefirst and second conductors and which have an exposed portion. Theheader/connector assembly also has a housing having an inlet port, a damin the space between the first and second conductors and urethane or asilicone rubber compound around the ends of the first and secondconductors. Header pins are connected to the first and second conductorsand to the connector pins.

Moreover, disclosed above is a method for sealing a rod-in-tube devicefor mounting on a vehicle which comprises providing the device with acavity having at least one inlet port and at least one narrow outflowpassage, injecting a curable compound through the inlet port(s) suchthat each narrow passage remains open during the injection process untilthe cavity is substantially full permitting air within the cavity to bedisplaced by the curable compound and curing the compound. Each passageis sufficiently narrow as to permit only a small amount of rubbercompound to flow out of the cavity during the injection process, butlarge enough to permit air to easily flow out of the assembly.

When the device is a crush velocity detecting sensor in accordance withthe invention comprising an electrically conductive tube and anelectrically conductive rod arranged within the tube and spacedtherefrom, the cavity is formed at least partially between the tube andthe rod. Also, a plurality of cavities can be formed between discreteregions of the tube and the rod, separated by means of spacers, andconnected through an aperture in the spacers to enable the injectedcurable compound to flow into each of the cavities.

The crush sensing crash sensor of this invention is ideally adapted forinstallation in the forward part of the crush zone for frontal, side andrear impacts of automobiles equipped with one or more inflatablepassenger protective airbags. When the vehicle is subjected to a crashof sufficient magnitude as to require the deployment of the passiveprotective device, a portion of the vehicle is crushed until it contactsthe sensor. At least a portion of the sensor deforms by bending orcrushing due to the forces exerted on it by the material contacting it.In a preferred embodiment, the sensor is constructed from a long rod anda tube with the rod positioned in the center of the tube by means ofinsulating spacers or as a coaxial cable. When the tube bends, thespacing of the rod between the spacers approached the tube at a velocitythat is representative of the crush velocity, which can be measured bythe change in impedance between the rod and tube.

The rod and tube assembly can be formed in any convenient geometry, asdiscussed above, during manufacture so as to conform to the possiblemounting locations in the crush zone of the vehicle. In this manner, thesensor is placed in the proper position to catch all crashes to thevehicle for which it was designed regardless of where on the vehicle theimpact takes place.

Other embodiments of the vehicle crush velocity detecting device inaccordance with the invention include an electrically conducting,deformable tube, an electrically conducting rod positioned within theelectrically conducting tube, and insulating devices positioned at leasttwo points between the rod and the tube to insulate the rod from thetube. When the tube is deformed or bent by a force greater than apredetermined magnitude, e.g., by the crush of the vehicle proximate toor at the location at which the device is placed, it is forced to movecloser to the rod. In a similar manner, the outer conductor of a coaxialcable is forced to move closer to the inner conductor.

In use as a side impact crush velocity measuring system in order todeploy an occupant protection apparatus for protecting an occupant in aside impact, the device is mounted in a position at the side of thevehicle so as to detect crush velocity of the side of the vehicle andthe crush velocity detecting device is coupled to the occupantprotection apparatus such that upon a threshold crush velocity theoccupant protection device is deployed. To this end, the crush velocitydetecting device has an elongate portion mounted in a positionsubstantially parallel to a door panel in a door on the side of thevehicle.

In another embodiment, the vehicle crash velocity sensor systemcomprises a crush velocity detecting device changeable from a higherimpedance position indicative of a non-crush situation and a lowerimpedance position indicative of crush of a portion of the vehicleproximate to the device, and an electronic sensor coupled to the crushvelocity detecting device and comprising an accelerometer, and a devicecoupled to the accelerometer, e.g., a microprocessor having analgorithm, for initiating deployment of the occupant protection devicebased on a velocity change of the crush detecting device and an analysisof output from the accelerometer indicative of a situation in whichdeployment of the occupant protection device is desired.

The crush velocity detecting sensor may comprise an electricallyconducting, deformable tube, an electrically conducting rod positionedwithin the electrically conducting tube and insulating devicespositioned at least two points between the rod and the tube to insulatethe rod from the tube. It may also comprise a coaxial cable having anouter and an inner conductor.

Furthermore, disclosed above is a method for sealing a device formounting on a vehicle, e.g., the crush velocity detecting device,comprising: assembling the device creating an enclosed cavity therein,injecting an uncured rubber compound through at least one inlet port ofthe cavity in such a manner that at least one narrow passage leadingfrom the cavity to an exterior thereof remains open during the injectionprocess until the cavity is substantially full permitting air within thecavity to be displaced by the rubber compound and curing the rubbercompound The passage is sufficiently narrow as to permit only a smallamount of rubber compound to flow out of the assembly during the fillingprocess, but large enough to permit air to easily flow out of theassembly. When the device is a crush velocity detecting sensor, it maycomprise an electrically conductive tube and an electrically conductiverod arranged within the tube and spaced therefrom in which case, thecavity is formed between the tube and the rod. Also, it is possible toform a plurality of cavities between discrete regions of the tube andthe rod, separating the cavities by means of spacers, and connecting thecavities through an aperture in the spacers to enable the injecteduncured rubber compound to flow into each cavity.

More particularly, disclosed above is a vehicle crush detecting devicein combination with a vehicle comprising an electrically conducting,deformable tube, an electrically conducting rod positioned within thetube, insulating devices positioned at least two points between the rodand the tube for insulating the rod from the tube and an attachmentmechanism for attaching the tube to the vehicle at least two spacedapart locations to provide at least one free, unrestrained span of thetube between the at least two spaced apart locations which is spacedaway and not in contact with any portion of the vehicle. When the tubeis deformed by a force greater than a predetermined magnitude duringcrush of the vehicle, the tube approaches the rod in response to thecrush of the vehicle thereby, through monitoring electronics, thevelocity of the crash can be determined.

The rod and tube in the sensor may be unitary and the rod maysubstantially solid. The insulating devices may comprise spacersextending circumferentially about the rod only at discrete locations inthe tube. A mounting mechanism may be provided for mounting the crushdetecting device in a front, side and/or rear regions of the vehicle soas to detect crush of the vehicle in any of these regions. If thevehicle includes a deployable occupant protection apparatus forprotecting an occupant in a side impact, a mounting mechanism may beprovided for mounting the crush detecting device in a side of thevehicle so as to detect the crush velocity of the side of the vehicle.Also, the crush detecting device is coupled to the occupant protectionapparatus such that upon completion of the electronic circuit, theoccupant protection device is deployed. An electromechanical sensorhaving a moving mass or an electronic sensor can be coupled to the crushvelocity sensor. The crush velocity detecting device may have anelongate portion mounted by the mounting mechanism in a positionsubstantially parallel to a door panel in a door on the side of thevehicle.

In another embodiment of the invention, the vehicle crush detectingdevice in combination with a vehicle comprises an electricallyconducting, deformable tube containing grease, an electricallyconducting rod positioned within the tube and insulating devicespositioned at least two points between the rod and the tube forinsulating the rod from the tube. When the tube is deformed by a forcegreater than a predetermined magnitude during crush of the vehicle, itmoves toward the rod during which time the crash velocity can bedetermined. Later, it can contact the rod and thereby complete anelectric circuit indicative of crushing of the vehicle. The tube is notcompletely filled with grease such that a few small voids are present inthe tube to allow for differential expansion between the grease and thetube.

In another embodiment of the invention, a vehicle crush velocitydetecting device in combination with a vehicle comprises an elongate,electrically conducting, deformable tube, the tube having an innercircumferential surface and an outer circumferential surface, anelongate, electrically conducting rod positioned within the tube andhaving an outer circumferential surface, an attachment mechanism forattaching the tube to the vehicle at least two spaced apart locations toprovide at least one free, unrestrained span of the tube between thespaced apart locations which is spaced away and not in contact with anyportion of the vehicle and an insulating mechanism positioned at leasttwo longitudinal points between the rod and the tube for insulating therod from the tube. The insulating mechanism is arranged to separate theentire outer circumferential surface of the rod from the entire innercircumferential surface of the tube around the entire outercircumference of the rod. As such, the tube is deformable by the crushof the vehicle about its entire circumference into contact with the rod.

When the tube is deformed by a force greater than a predeterminedmagnitude during crush of the vehicle, it approaches the rod at avelocity indicative of the crash velocity which is measured byappropriate electronic circuitry and then contacts the rod therebycompleting an electric circuit indicative of crushing of the vehicle.

In one preferred embodiment of the invention, an elongate sensor such asa coaxial cable stretches from the driver side door near the B-pillarthrough the A-pillar, across the front of the vehicle and into thepassenger side door. A signal having a frequency on the order of about10 megahertz is imposed on the cable, which frequency is selected sothat approximately the cable is approximately one wavelength long (thusthe frequency could vary depending on the length of the cable). Thecable is terminated at the far end with a known resistance. Under normaloperation, the wave travels down the cable and reflects off of the endand returns in phase with the transmitted pulse. If, however, the cableis compressed along its length a reflected wave will be returned that isout of phase with the transmitted wave.

By comparing the phase of the reflected wave with the transmitted wave,the location of the compression can be determined and by comparing themagnitude of the reflection, the amount of compression can bedetermined. By measuring the amount of compression over time, thevelocity of compression can be found. Thus, the location of the impactand the crush velocity (which can be considered a function of thevelocity of compression) can both be determined by this sensor for bothside and frontal impacts. A similar sensor could be designed for use insensing side and rear impacts.

More generally, a crash sensor arrangement for determining whether thecrash involving the vehicle requires deployment of the occupantrestraint device comprises an elongate sensor arranged in the crush zoneto provide a variable impedance as a function of a change in velocity ofthe crush zone and a processor for measuring the impedance of the sensoror a part thereof at a plurality of times to determine changes in theimpedance of the sensor or part thereof. The processor provides a crashsignal for consideration in the deployment of the occupant restraintdevice based on the determined changes in impedance of the sensor orpart thereof. The sensor can have a U-shaped portion extending alongboth sides of the vehicle and across a front of the vehicle, and thussubstantially completely between opposed longitudinal edges of a door ofthe vehicle.

In the embodiment wherein the sensor comprises a coaxial cable, anelectromagnetic wave generator generates electromagnetic waves and feedsthe waves into the cable and the processor is preferably embodied in anelectronic control module coupled to the electromagnetic wave generator.The electromagnetic wave generator preferably feeds electromagneticwaves into the cable having a wavelength on the same order as a lengthof the cable. In the alternative, the sensor can comprise parallelstrips of conductive material spaced apart from one another in theabsence of deformation of the crush zone and arranged to contact oneanother during deformation of the crush zone. The contact strips arepositioned so as to be compressed during deformation of the crush zonewhereby such compression causes changes in impedance of the sensor.

Another method of determining the deflection of the periphery of avehicle that can be used as a crash sensor is to use the bend sensorprinciples as reported in U.S. Pat. No. 6,497,430 mass profiling system.Such devices can be placed on or inside of the vehicle skin and measurethe relative deflection of a portion of the vehicle during a crash.

1.5 Side Impact Sensor Systems

FIGS. 37 and 38 show an all-mechanical self-contained airbag system formounting on the side of a vehicle to protect occupants in side impactsin accordance with the invention which is designated generally as 320.The airbag system 320 contains one or more inflatable airbags 322, aninflator assembly 323, a mounting plate 343 for mounting the airbagsystem 320 on the side of the vehicle and a sensor assembly 334 mountedto the inflator assembly 323. The sensor assembly 334 contains arotatable, substantially planar sensing mass 335 and a cantileveredbiasing spring 336 which performs the dual purposes of biasing thesensing mass 335 toward its at rest position shown in FIG. 38 and alsoproviding the energy to the firing pin 337 required to initiate a stabprimer 325 as further described below. The sensing mass 335 contains afiring pin spring-retaining portion 338 that restrains the firing pin337 during the sensing time and releases it when the sensing mass 335has rotated through the sensing angle. The retaining portion 338 is anL-shaped descending part formed on a planar surface of the sensing mass335 and defines a cavity for retaining an end of the spring 336.

As shown in FIG. 37, the mounting plate 343 constitutes a housing forthe airbag system 320, i.e., it has a bottom wall and flanged side wallsextending from edges of the bottom wall which define an interior spacein which the airbag(s) 322 and a portion of the inflator assembly 323are arranged. The bottom wall is substantially flat and has asubstantially circular aperture. The inflator assembly 323 is positionedin the aperture so that a portion thereof extends on either side of thebottom wall (FIG. 38). Also as shown in FIG. 38, the housing of theinflator assembly 323 includes a flange that abuts against the bottomwall of mounting plate 343 around the aperture. As will be appreciatedby those skilled in the art, the flanged side walls of the mountingplate 343 are positioned around a panel on the side of the vehicle,e.g., a blow-out panel in the side door, so that the airbag(s) 322 wheninflating will be expelled from the interior space defined by themounting plate 343 into the passenger compartment of the vehicle. Themounting plate 343 may thus be mounted to a frame of the side door byattaching the flanged side walls to the frame or attaching anotherportion of the mounting plate to the frame. The actual manner in whichthe mounting plate 343 is mounted in the side door, or on the side ofthe vehicle, is not critical so long as the mounting plate 343 ispositioned to allow the airbag(s) 322 to be expelled from the interiorspace into the passenger compartment. Mounted as such, the sensorassembly 334 will be most proximate the exterior of the vehicle with theairbag 322 most proximate the passenger compartment of the vehicle.

The sensing mass 335 is connected to the housing 321 of sensor assembly334 through a hinge 339 at one end whereby the opposed end isunrestrained so that the sensing mass 335 rotates about the hinge 339.In view of the mounting of the airbag system 320 on the side of thevehicle, hinge 339 defines a rotation axis which is perpendicular to thelongitudinal direction of travel of the vehicle (x) as well asperpendicular to a direction (y) transverse to the longitudinaldirection of travel of the vehicle, i.e., it is a vertical axis (z).

The sensor housing 321 includes opposed housing wall portions 340 and341, a top cover 342 and a bottom cover 364 which is connected to,mounted on or the same part as a top cover 324 of the inflator assembly323. The sensor housing 321 is filled with air and sealed (whenappropriately mounted to the inflator assembly 323 whereby a smallorifice 330 in bottom cover 346 is closed by the inflator assembly 323)so as to maintain a constant air density regardless of the ambienttemperature or pressure. The sensor housing walls 340,341 and sensingmass 335 are preferably molded along with the hinge 339 in a singleinsert molding operation to provide a careful control of the dimensionsof the parts and particularly of a clearance 345 between the walls340,341 and the sensing mass 335 for the reasons described below.

The inflator assembly 323 comprises a stab primer 325, igniter mix 333associated with the stab primer 325, one or more propellant chambers 326containing propellant 327 and a series of cooling and filtering screens328. In the particular design shown in FIGS. 37 and 38, the stab primer325 has been placed inside of an igniter housing portion 329 of thehousing of the inflator assembly 323, the housing of the inflatorassembly being formed by opposed housing sections 324 and 332. Housingsections 324 and 332 cooperate to define a substantially cylindricalhousing for the inflator assembly 323. Housing section 324 is coupled tothe sensor housing 321. Exit orifices 331 are provided in the housingsection 332 to allow the gas generated by the burning propellant 327 toflow into the airbag 322 to inflate the same. A small orifice 330 hasbeen left open in the bottom cover 346 of the housing 321 of the sensorassembly 334, as well as the housing section 324, to allow the firingpin 337 to enter into the interior of the inflator assembly 323 andcause initiation of the stab primer 325. The stab primer 325 is from afamily of the most sensitive stab primers requiring less than 25 in-ozof energy for activation. The standard M55 military detonator is amember of this class and has been manufactured in very large quantitiesduring war time. For the purposes of this disclosure, the term primerwill be used to represent both primers and detonators. The small orifice330 will permit some gas to enter the sensor housing 321 during the timethat the propellant 327 is burning and inflating the airbag 322 butsince its area is less than 1% of the area of the exit orifices 331through which the generated gas enters the airbag 322, less than 5% ofthe generated gas will pass into the sensor. Naturally, a larger orificecould be used but in all cases the amount of gas which passes into thesensor housing 321 will be less than 10% of the total gas generated.Since this gas will be hot, however, it will destroy the sensor assembly334 and leak into the door. In another implementation discussed below, athrough bulkhead initiation system is used to prevent any gas frompassing into the sensor assembly from the inflator assembly.

During operation of the device, sensing mass 335 rotates relative tosensor housing 321 in the direction of the arrow (FIG. 38) under theinfluence of the acceleration with its motion being retarded by thebiasing spring 336 and the gas pressure forces. Upon a sufficientrotation, biasing spring 336 is released from the retaining portion 338of the sensing mass 335 and moves toward the inflator assembly 323 andthe firing pin 337 formed in connection with the biasing spring 336moves to impact stab primer 325 which burns and ignites the igniter mix333. The igniter mix, which is typically composed of boron and potassiumnitrate, then ignites the propellant 327 that burns and generates gas.The gas then flows through exit orifices 331 into the inflatable bag322, inflating the bag.

In the embodiment shown in FIGS. 37 and 38, the stab primer 325 has beenlocated in the center of the inflator housing. This is the conventionallocation for electrical primers in most driver side inflator designs.The sensor is placed adjacent and in line with the inflator permittingthe use of conventional inflator designs which minimize the size,complexity and weight of the inflator. The sensing mass 335 isapproximately of square shape and the sensor housing 321 is madecircular to mate with the inflator design.

In the particular design shown in FIGS. 37 and 38, a burning propellantinflator design was illustrated. Naturally, other propellanttechnologies such as a stored gas or hybrid (a combination of stored gasand propellant) could have been used without departing from theteachings of this invention.

It will be appreciated by those skilled in the art that since the airbagsystem 320 is designed to activate in side impacts, the sensing mass 335is arranged for movement in a direction perpendicular to the sides ofthe vehicle, i.e., perpendicular to the longitudinal direction of travelof the vehicle, or in a pivoting movement about a vertical pivot axis.In this manner, the acceleration of the sensor housing 321 inward intothe passenger compartment (that is, acceleration in a lateral directionor lateral acceleration since the passenger compartment is inward fromthe sensor housing relative to the side of the vehicle in theillustrated embodiment) resulting from a crash into the side of thevehicle, will cause the sensing mass 335 to move or pivot outward towardthe impacting object thereby releasing its hold on the biasing spring336.

FIG. 39 shows a fragmentary view of a sensing mass 352 and an attachedlever arm 353 extending from a D-shaft 354 prior to rotation of thesensing mass incident to a crash as adapted to the all-mechanical systemof Thuen, U.S. Pat. No. 4,580,810. This figure corresponds to FIG. 6 ofthe Thuen patent and shows the improved sensing mass design. FIG. 40shows the same view as FIG. 39 with the sensing mass rotated, under thetorque from spring 355 acting on ball 359, into the actuating positionwhere it has released the firing pin to initiate deployment of theairbag. FIG. 40 corresponds to FIG. 7 in the '810 patent. FIG. 41 is aview taken along line 41-41 of FIG. 40 and shows the shape of thesensing mass 352. Sensing mass 352 is retained in sensor housing 350, bycover 351, and rotates with D-shaft 354. This rotation is facilitated bypivots 357, which form part of the D-shaft, and pivot plates 356. Inthis manner, the sensing mass 352 is hinged to the sensor housing 350permitting only rotational motion and rendering the sensor insensitiveto the effects of cross-axis accelerations. In this embodiment, sensingmass 352, lever arm 353, ball 359, pin 358 and the D-shaft 354 are allmade as one part that reduces the cost of the assembly. Naturally, theycould be made as separate parts and assembled. When D-shaft 354 rotatesthrough a sufficient angle, it releases firing pin 349 in the samemanner as shown in FIGS. 8 and 9 of the '810 patent. The motion of thesensing mass 352 is undamped since the clearance between the sensingmass 352 and sensor housing 350 is sufficiently large so as to minimizethe flow resistance of the air as the mass rotates. Naturally, inanother implementation, the mass could be redesigned to have its motiondamped by the flow of a gas in the manner shown in FIGS. 37 and 38above. Also, two sensor systems of the type disclosed in FIGS. 39-41 canbe used in the all-mechanical system in a similar way as shown in the'810 patent.

The all-mechanical system as depicted in FIGS. 39-41 requires that aspecial inflator be designed to accommodate the sensor within itshousing. There has already been a substantial investment in tooling andproduction facilities for electrically actuated inflators by severalinflator manufacturers. Also, substantial reliability statistics havebeen accumulated on these inflator designs through the hundreds ofmillions of miles that airbag equipped vehicles have traveled. It isdesirable to build on this base with new systems that can be done usingthe sensor designs of this invention as depicted in FIGS. 42 and 43.This sensor design is adapted to be attached to a standard electricalinflator design where a stab primer 373 is used in place of theelectrically actuated squib normally used.

The sensor-initiator is shown generally as 360 in FIG. 42. In a similarmanner as described above, sensing mass 364 rotates in sensor housing361 during a crash against the force provided by a cantilevered biasingspring 366 until a D-shaft 365 has rotated sufficiently to release afiring pin 363. Once released, firing pin 363 is propelled by firing pinspring 362 and impacts primer 373 to initiate deployment of the airbag.A washer containing an orifice 374 is provided in the top of primer 373to minimize the leakage of inflator gases from the inflator 372 whilethe propellant is burning (FIG. 43). In this manner, the sensor does nothave to be constructed of strong materials as discussed in the abovereferenced patent.

In one configuration of a self-contained system, the sensor assembly andthe airbag and inflator assembly are kept separate until mounted ontothe vehicle. In this case, the sensor is mounted using an appropriateapparatus (not shown) to the steering wheel after the wheel is mountedto the vehicle. Then, the airbag module is assembled to the steeringwheel. In this case, the sensor is armed after it has been installedonto the vehicle through the use of arming screw 367. The inflator isonly brought into contact with the sensor after the sensor has beenmounted onto the vehicle, thus minimizing the chance of an inadvertentactuation prior to installation. To arm the sensor, arming screw 367 isrotated after the sensor is mounted onto the steering wheel causing itto move downward in its housing 369. This removes the retaining cylinder368 from blocking the motion of locking ball 370 that removes a lock onthe firing pin. As long as ball 370 remains locking the firing pin 363,rotation of the mass 364 will not release the firing pin and the sensoris unarmed. Additional apparatus, not shown, can be used to prevent theassembly and disassembly of the sensor from the steering wheel unlessthe arming screw 367 is in the unarmed position. Also, interferencebetween the head 371 of the arming screw 367 and the surface 375 of theinflator 372 prevents assembly of the inflator and airbag module to thesteering wheel until the sensor has been armed. Thus, in this verysimple manner, an inexpensive all-mechanical airbag system can be madeusing standard inflator designs with minor modifications.

In FIGS. 37 and 38, the stab primer was shown as part of the inflatorassembly, i.e., contained within the housing of the inflator assemblydefined by housing portions 324,332. On the other hand, in FIG. 44. across section view of a through bulkhead initiation system adapted to amechanical self-contained airbag system is illustrated. In this case,the stab primer 378 is instead part of a sensor assembly 380, i.e.,arranged in the sensor housing on the bottom cover thereof if present,and when the stab primer 378 is initiated by a firing pin 381 formed inconjunction with a cantilevered, biasing spring (as in the embodimentshown in FIGS. 37 and 38), it creates a shock on one side of an inflatorhousing wall 377 which is transmitted through the wall and interactswith a shock sensitive pyrotechnic mix 379 which has been placed into acavity 376 in the igniter mix. Inflator housing wall 377 is alongsidethe bottom cover of the sensor housing, but in the alternative, theinflator housing wall may be the same as the bottom cover of the sensorhousing. This through-bulkhead initiation system and the particularpyrotechnic mix formulation is well known to ordinance engineers whereit has been applied to military devices. Such a system has not beenused, however, in airbag systems. In this manner, a hole is not openedbetween the sensor assembly and the inflator assembly and the gas isprevented from leaking into the sensor assembly.

In FIG. 45, a perspective view of a mechanical self-contained airbagsystem using a crush sensing arming system designated generally as 385is shown in the state before a crash occurs. In this embodiment, thesensor is armed when the vehicle door skin, or side skin, is crushed towhere it impacts a curved impact plate, not shown, which then impacts asensor can 387 surrounding the sensor assembly and displaces an outercover 386 thereof relative to a sensor housing 382. Sensor can 387 has atubular wall arranged partially alongside a housing section of theinflator assembly to thereby define a closed space between the outercover 386 and an outer surface of the inflator assembly in which thesensor assembly is positioned. The sensor crush-sensing outer cover 386has a slight arcuate shape so that it oil-cans downward pressing onlever 388 through a hemi-spherical pusher member 394. Lever 388 ishingedly mounted at one end thereof to enable it to rotate about itsattachment point 389 to the sensor housing 382 and causes lever 390 toalso rotate about its pivot point 391 on the sensor housing 382 byvirtue of hinge 393. An end 392 of lever 390 extends through an aperture395 in a wall of the sensor housing 382 and serves to restrain thesensing mass 383 from any movement (FIG. 46). The rotation of lever 390causes the end 392 of lever 390 to pull out of the sensor housing 382where it was detenting the sensing mass 383 and preventing the sensingmass 383 from rotating to the degree necessary to release a firing pinspring 384. The sensing mass 383 is then free to move and release thefiring pin spring 384 causing the firing pin spring 384 to ignite thestab primer in the inflator assembly, either by contact therewith or bypressure against the inflator assembly housing (see above) causinginflation of the airbag (FIG. 47A). Thus, until the sensor experiences acrushing force from the crash, the airbag system cannot deploy. Thesensing mass 383, firing pin spring 384, inflator assembly and airbagmay have the same structure as described above with reference to FIGS.37 and 38. Other features of any of the disclosed embodiments notinconsistent with the embodiments shown in FIGS. 45-47 may also beincorporated therein.

Levers 388 and 390 are joined together by hinge 393 and can be made froma single piece of material. In this case, the hinge would be formedeither by a coining or stamping operation or by a milling operation.Naturally, the two levers need not be joined together.

This provides a sensor system that requires the occurrence of twoenvironments that are always present in a crash, crush and velocitychange. The crush sensing outer cover 386 is designed to respond and armthe sensor when impacted from any reasonable direction by an impactplate (not shown) which is likely to occur in a crash. For manyvehicles, the crush may not reach the sensor at the time that deploymentis required. In the case where two systems are used on each side of thevehicle, for example, and an impact occurs at the A-pillar, the rearseat system may not experience crush in time. The arming system shown inFIG. 45 could still be used where the arming would occur when the systemis mounted onto the vehicle instead of when the crash occurs. In thiscase, the curved impact plate would not be necessary and the deflectionof the sensor cover would occur either during the mounting process or bya separate operation after the system is mounted.

FIG. 46 is a cross section view of the apparatus of FIG. 45 taken alonglines 46-46 showing the crush sensing outer cover 386 and lever systemafter end 392 has moved out of aperture 395 as a result of crush of thevehicle but before the sensing mass 383 of the discriminating sensor hasbegun to move. FIG. 47 is a similar view of the apparatus of FIG. 46 butshows the sensing mass 383 of the discriminating sensor after it hasmoved and released firing pin 381, triggering the inflation of theairbag.

The motion of the sensing mass 383 is damped by the requirement that airmust flow between the sensing mass and the housing in the mannerdescribed in more detail in the '253 patent referenced above. Naturally,other damping methods such as magnetic damping could also be used.

In the case of FIG. 45, the sensor is entirely surrounded by a metal can387 that is formed by a drawing process. The sensor can 387 is attachedto the inflator assembly; more particularly, the sensor can 387 isattached to one or more housing sections thereof. The attachment of thesensor can 387 to the inflator assembly or housing section(s) thereof isachieved using structural adhesive such as a urethane or epoxy compound.In this manner, the sensor is hermetically sealed.

The term hermetic seal as used herein means a seal which will not permitthe passage of any significant amount of moisture or other contaminantsinto the interior of the self-contained airbag module and further willnot permit the passage of gas into or out of the sensor housing ofsufficient quantity as to change the gas density by more than about 5%at any time over the life of the vehicle. Each vehicle manufacturer hasan accelerated life test that can be used along with appropriate sensortesting equipment to test the sensor seals according to this definition.Typical O-ring seals are not hermetic by this definition howeverproperly designed plastic and metal welded seals and epoxy and urethaneseals are hermetic.

FIG. 48 is a perspective view of a side impact airbag systemillustrating the placement of the airbag vents in the door panel and theexhausting of the inflator gases into the vehicle door 399 and alsoshowing the use of a pusher plate 400 to adjust for the mismatch betweenthe point of impact of an intruding vehicle (or other object) and thesensor of a self-contained side impact airbag system 402. The pusherplate 400 is shown attached to the main structural door beam 401 in thisillustration but other mounting systems are also possible. The airbagsystem 402 is shown between the inner panel 403 and the outer panel 404of the door 399.

The pusher plate 400 is dimensioned and installed in the door 399 sothat during a side impact to any portion of the side of the vehiclewhich is likely to cause intrusion into the passenger compartment andcontact an occupant, the pusher plate will remain in a substantiallyundistorted form until it has impacted with the sensor causing thesensor to begin deployment of the airbag. In this implementation, anon-sodium azide propellant, such as nitro-cellulose, is used and thegas is exhausted into the door though a pair of orifices. The airbagsystem 402 may be any of those disclosed herein. As shown in FIG. 48,the pusher plate 400 may be circular.

FIG. 49 is a cross-sectional view of a self-contained side impact airbagsystem using an electro-mechanical sensor. An electro-mechanical sensoris one in which the sensing is accomplished through the motion of asensing mass from a first at-rest position to a second activatingposition at which point an event happens which typically involves theclosing of a switch by mechanical or magnetic means. In the embodimentshown in FIG. 49, biasing spring contact 405 is caused to engage contact406 arranged on top cover when the sensor experiences a crash asdescribed above, i.e., acceleration of the sensor housing above apredetermined threshold value which results in movement of the sensingmass until the biasing contact 405 contacts the other contact 406.Specifically, the biasing spring contact 405 is positioned in a position(e.g., bearing against the sensing mass in the sensor housing) so thatit is moved during a crash along with movement of the sensing mass (inthe upward direction in FIG. 49) to thereby bring the biasing springcontact 405 into contact with contact 406. An electrical circuit isthereby completed causing ignition of the primer or squib and thereafterthe igniter mix and propellant. As shown in FIG. 49, the structure ofthe sensor housing 407, inflator assembly 408, the mounting plate andsensing mass may be as described above in appropriate part.

The implementation of FIG. 49 is a preferred location for theself-contained airbag module of this invention. Naturally, some of theteachings of this invention can be practiced without necessitating aself-contained module. For some implementations, for example, it isdesirable to place the airbag module at some other location than thevehicle door. One such location, for example, is the vehicle seat. Forthis implementation, the crash sensor in general cannot be co-locatedwith the airbag module. Therefore, it can be mounted on the side of thevehicle or elsewhere as long as there is a sufficiently strong memberconnecting the crash sensor to the vehicle side such that there islittle or no plastic deformation between the sensor and the side of thevehicle. Thus, the sensor experiences essentially the same crash signalas experienced by the side of the vehicle. Through this technique, thesensor acts as if it were mounted on the side of the vehicle and yet thewiring does not have to go through the door and through the hinge pillarto the airbag module. In this way, the sensor can be mounted remote fromthe vehicle side and yet perform as if it were located on the vehicleside which is accomplished by using an extension of the sensor, whichcan be a structural member of the vehicle.

FIG. 50 is a cross-sectional view of a self-contained side impact airbagsystem using an electronic sensor that generates a signal representativeof the movement of a sensing mass. Unless otherwise stated orinconsistent with the following description of an airbag system with anelectronic sensor, the airbag system with an electronic sensor mayinclude the features of the airbag system described above and below. Anelectronic sensor is one in which the motion of the sensing mass istypically continuously monitored with the signal electronicallyamplified with the output fed into an electronic circuit which isusually a micro-processor. Electronic sensors typically useaccelerometers that usually make use of strain gage or piezoelectricelements shown here as 409. The piezoelectric element generates a signalrepresentative of the movement of the sensing mass. Modernaccelerometers are sometimes micro-machined silicon and combined withother elements on an electronic chip. In electro-mechanical sensors, themotion of the sensing mass is typically measured in millimeters and ismuch larger than the motion of the sensing mass in electronic sensorswhere the motion is frequently measured in microns or portions of amicron. The signal representative of the motion of the sensing mass isrecorded over time and an algorithm in the micro-processor may bedesigned to determine whether the movement over time of the sensing massresults in a calculated value which is in excess of the threshold valuebased on the signal. The sensing mass may constitute part of theaccelerometer, e.g., the sensing mass is a micro-machined accelerationsensing mass. In this case, the microprocessor determines whether themovement of the sensing mass over time results in an algorithmicdetermined value that is in excess of the threshold value based on thesignal.

In embodiments using an electronic sensor, the inflator may include aprimer which is part of an electronic circuit including theaccelerometer such that upon movement over time of the sensing massresults in a calculated value in excess of the threshold value, theelectronic circuit is completed thereby causing ignition of the primer.

When the term electrical as used herein it is meant to include bothelectro-mechanical and electronic systems.

FIG. 51 is a schematic of the electric circuit of an electro-mechanicalor electronic side impact airbag system. The self-contained moduleimplementation shown generally at 410 contains a sensor assembly 421 andan airbag and inflator assembly 418. The sensor assembly 421 contains asensor 422, a diagnostic module 423, an energy storage capacitor 424,and a pair of diodes 420 to prevent accidental discharge of thecapacitor if a wire becomes shorted. The module is electricallyconnected to a diagnostic monitoring circuit 425 by wire 411 and to thevehicle battery 426 by wire 413. It is also connected to the vehicleground by wire 412. The sensor, diagnostic and capacitor power suppliesare connected to the squib by wires 415 through 417.

In a basic configuration, the diagnostic monitoring circuit 425 checksthat there is sufficient voltage on the capacitor to initiate theinflator in the event of an accident, for example, and either of wires411, 412, 413 or 414 are severed. In this case, the diagnostic internalto the self-contained module would not be necessary. In moresophisticated cases, the diagnostic module 423 could check that thesquib resistance is within tolerance, that the sensor calibration iscorrect (through self testing) and that the arming sensor has notinadvertently closed. It could also be used to record that the armingsensor, discriminating sensor and airbag deployment all occurred in theproper sequence and record this and other information for futureinvestigative purposes, e.g., in a “black box”. In the event of amalfunction, the diagnostic unit could send a signal to the monitoringcircuitry that may be no more than an indication that the capacitor wasnot at full charge.

A substantial improvement in the reliability of the system may beachieved by placing the diagnostic module and backup power supply withinthe self-contained airbag system particularly in the case of sideimpacts where the impact can take place at any location over a widearea. An impact into a narrow pole at the hinge pillar, for example,might be sufficient to sever the wire from the airbag module to thevehicle power source before the sensor has detected the accident.

Most of the advantages of placing the sensor, diagnostic and backuppower supply within the self-contained module can of course be obtainedif one or more of these components are placed in a second module inclose proximity to the self-contained module. For the purposes ofelectro-mechanical or electronic self-contained modules, therefore, asused herein, the terms “self-contained module” or “self-contained airbagsystem” will include those cases where one or more of the componentsincluding the sensor, diagnostic and backup power supply are separatefrom the airbag module but in close proximity to it. For example, in thecase of steering wheel mounted systems, the sensor and backup powersupply would be mounted on the steering wheel and in the case of sideimpact door mounted systems, they would be mounted within the door orseat. In conventional electrical or electronic systems, on the otherhand, the sensor, diagnostic module and backup power supply are mountedremote from the airbag module in a convenient location typicallycentrally in the passenger compartment such as on the tunnel, under theseat or in the instrument panel.

With the placement of the backup power supply in the self-containedmodule, greater wiring freedom is permitted. For example, in some casesfor steering wheel mounted systems, the power can be obtained throughthe standard horn slip ring system eliminating the requirement of theribbon coil now used on all conventional driver airbag systems. For sideimpact installations, the power to charge the backup power supply couldcome from any convenient source such as the power window or door lockcircuits. The very low resistance and thus high quality circuits andconnectors now used in airbag systems are not required since even anintermittent or high resistance power source would be sufficient tocharge the capacitor and the existence of the charge is diagnosed asdescribed above.

Herein, the terms capacitor, power supply and backup power supply havebeen used interchangeably. Also, other energy storage devices such as arechargeable battery could be used instead of a capacitor. For thepurposes of this disclosure and the appended claims, therefore, the wordcapacitor will be used to mean any device capable of storing electricalenergy for the purposes of supplying energy to initiate an inflator.Initiation of an inflator will mean any process by which the filling ofan airbag with gas is started. The inflator may be either purepyrotechnic, stored gas or hybrid or any other device which provides gasto inflate an airbag.

As discussed above, FIG. 25 is a side view showing the preferredmounting of two self-contained airbag modules 212 and 213 on the side ona two door vehicle. Module 212 is mounted inside of a door, whereby thesensor housing of module 212 is most proximate the exterior of thevehicle, while module 213 is mounted between the inner and outer sidepanels at a location other than the door, in this case, to protect arear seated occupant. Each of the modules has its own sensor and, in thecase of electrical self-contained systems, its own capacitor powersupply and diagnostic circuit. Any of the airbag systems disclosedherein may be mounted either inside a door or between inner and outerside panels of the vehicle at a location other than the door and for nonself-contained systems, the sensor can be mounted anywhere providedthere is a sufficiently strong link to the vehicle side so that thesensor is accelerated at a magnitude similar to the vehicle side crushzone during the first few milliseconds of the crash. In view of themounting of module 213 between inner and outer panels of the vehicle ata location other than the door, the inner and outer panels are thusfixed relative to the vehicle frame and the module 213 is also thusfixed relative to the frame. By contrast, the module 212 mounted insidethe door is moved whenever the door is opened or closed.

Thus, disclosed above is a vehicle including a side impact crash sensor,a transfer structure interposed between the side of the vehicle and thesensor, and an occupant restraint device such as a side impact airbagsystem. When an object strikes the side of the vehicle, the transferstructure transfers the lateral force from the side of the vehicle tothe sensor. The side impact crash sensor detects the lateral force oracceleration applied to a side of the vehicle. The airbag system isconnected to the sensor and arranged to deploy based on the force oracceleration detected by the sensor. The transfer structure may be aplate, and is optionally arranged to adjust for a mismatch between thepoint of impact of an object on the side of the vehicle and the sensor.The plate may be mounted on a main structural beam in the vehicle, suchas the main structural beam of the door of the vehicle. The entiresystem may be mounted between the inner and outer panels of the door ofthe vehicle. In another embodiment, there is a mismatch adjustmentstructure in place of or in combination with the transfer structure.

The side impact crash sensor for a vehicle may include a housing, a masswithin the housing movable relative to the housing in response toaccelerations of the housing, structure responsive to the motion of themass upon acceleration of the housing in excess of a predeterminedthreshold value for controlling an occupant protection apparatus andstructure for mounting the housing in such a position and a direction asto sense an impact into a side of the vehicle. The sensor may be anelectronic sensor arranged to generate a signal representative of themovement of the mass and optionally comprise a micro-processor and analgorithm for determining whether the movement over time of the mass asprocessed by the algorithm results in a calculated value which is inexcess of the threshold value based on the signal. In the alternative,the mass may constitute part of an accelerometer, i.e., a micro-machinedacceleration sensing mass. The accelerometer could include apiezo-electric element for generating a signal representative of themovement of the mass.

With respect to the arrangement of the sensor, some non-limitingmounting locations include inside a door of the vehicle, between innerand outer panels not associated with a door of the vehicle, a seat inthe vehicle and remote from the side of the vehicle in which case, thevehicle should include a sufficiently strong member connecting thesensor to the vehicle side such that there is little or no plasticdeformation between the sensor and the side of the vehicle.

Another embodiment of the sensor comprises a sensor assembly responsiveto a side impact for controlling the occupant protection apparatus,i.e., the airbag(s). The sensor assembly comprises a sensor housing, amass arranged within the sensor housing and movable relative to thehousing in response to acceleration thereof and structure responsive tothe movement of the mass upon acceleration of the housing in excess of apredetermined threshold value for controlling deployment of theairbag(s). The assembly may be mounted onto a side door of the vehicleand/or a side of the vehicle between the centers of the front and rearwheels of the vehicle in such a position and a direction as to causemovement of the mass upon an impact into the side of the vehicle.Additional mounting possibilities include in contact with a side doorassembly of the vehicle and/or a side panel assembly of the vehiclebetween the centers of the front and rear wheels in such a position anda direction as to cause movement of the mass upon an impact into theside of the vehicle.

One embodiment of a side impact airbag system for a vehicle inaccordance with the invention comprises an airbag housing defining aninterior space, one or more inflatable airbags arranged in the interiorspace of the system housing such that when inflating, the airbag(s)is/are expelled from the airbag housing into the passenger compartment(along the side of the passenger compartment), and an inflator forinflating the airbag(s). The inflator usually comprises an inflatorhousing containing propellant. The airbag system also includes a crashsensor as described above for controlling inflation of the airbag(s) viathe inflator upon a determination of a crash requiring inflationthereof, e.g., a crash into the side of the vehicle along which theairbag(s) is/are situated. The crash sensor may thus comprise a sensorhousing arranged within the airbag housing, external of the airbaghousing, proximate to the airbag housing and/or mounted on the airbaghousing, and a sensing mass arranged in the sensor housing to moverelative to the sensor housing in response to accelerations of thesensor housing resulting from, e.g., the crash into the side of thevehicle. Upon movement of the sensing mass in excess of a thresholdvalue, the crash sensor controls the inflator to inflate the airbag(s).The threshold value may be the maximum motion of the sensing massrequired to determine that a crash requiring deployment of the airbag(s)is taking place.

The crash sensor of this embodiment, or as a separate sensor of anotherembodiment, may be an electronic sensor and the movement of the sensingmass is monitored. The electronic sensor generates a signalrepresentative of the movement of the sensing mass that may be monitoredand recorded over time. The electronic sensor may also include amicroprocessor and an algorithm for determining whether the movementover time of the sensing mass as processed by the algorithm results in acalculated value that is in excess of the threshold value based on thesignal.

In some embodiments, the crash sensor also includes an accelerometer,the sensing mass constituting part of the accelerometer. For example,the sensing mass may be a micro-machined acceleration sensing mass, inwhich case, the electronic sensor includes a micro-processor fordetermining whether the movement of the sensing mass over time resultsin an algorithmic determined value which is in excess of the thresholdvalue based on the signal. In the alternative, the accelerometerincludes a piezoelectric element for generating a signal representativeof the movement of the sensing mass, in which case, the electronicsensor includes a micro-processor for determining whether the movementof the sensing mass over time results in an algorithmic determined valuewhich is in excess of the threshold value based on the signal.

The inflator may be any component or combination of components which isdesigned to inflate an airbag, preferably by directing gas into aninterior of the airbag. One embodiment of the inflator may comprise aprimer. In this case, the crash sensor includes an electronic circuitincluding the accelerometer and the primer such that upon movement overtime of the sensing mass results in a calculated value in excess of thethreshold value, the electronic circuit is completed thereby causingignition of the primer.

Although several preferred embodiments are illustrated and describedabove, there are possible combinations using other geometries, materialsand different dimensions for the components that can perform the samefunction. For example, the biasing spring need not be the same as thebiasing spring in the case of the implementation shown in FIG. 37 and amagnet might be used in place of a biasing spring for several of themechanical cases illustrated. Therefore, this invention is not limitedto the above embodiments and should be determined by the claims.

1.6 Anticipatory Sensing

FIG. 18 illustrates a side impact anticipatory sensor system, shown hereincluding transducers 130-138 which can be situated in differentlocations on one side of the vehicle, using the same or a differentcomputer system or processor as discussed above, and coupled thereto bysuitable means (the other side of the vehicle can be provided with thesame arrangement). These transducers can be optical or infrared imagerssuch as two or three dimensional CMOS or CCD cameras, line cameras,laser radar (lidar or ladar) devices, ultrasonic sensors, radar devicesetc. These transducers can provide the data to permit the identificationof an object that is about to impact the vehicle at that side as well asits velocity and point of impact. An estimate can then be made of theobject's weight and therefore the severity of the pending accident. Thisprovides the information for the initial inflation of the side airbagbefore the accident begins. If additional information is provided fromthe occupant sensors, the deployment of the side airbag can be tailoredto the occupant and the crash in a similar manner as described above.

FIG. 18 also illustrates additional inputs that, in some applications,provide useful information in determining whether a side airbag shouldbe deployed, for example. These include inputs from a front-mountedcrash sensor 139 mounted on the vehicle radiator 140, an engine speedsensor 166, and a wheel speed sensor 141 as used in an antilock brakingsystem sensor.

The use of anticipatory sensing, as described above and in U.S. Pat. No.6,343,810 can be used in a Phase 4 Smart Airbag system. This can be donewith the anticipatory sensor acting in concert with or in place of theaccelerometer-based neural network crash sensor described above. In apreferred embodiment, both sensors are used with the anticipatory sensorforecasting the crash severity before the collision occurs and one ormore accelerometer based sensors confirm that forecast. The mass of theimpacting object, for example, can be anticipated and confirmed.

Collision avoidance systems currently under development use radar orlaser radar to locate objects such as other vehicles that are in apotential path of the subject vehicle. In some systems, a symbol can beprojected onto the windshield in a heads-up display signifying that someobject is within a possible collision space with the subject vehicle. Noattempt at present is made to determine what that object is and todisplay an image of the object. Neural network pattern recognitionsystems, as well as other pattern recognition systems, have thatcapability and future collision avoidance systems may need thiscapability. The same pattern recognition computer system that isproposed here for sensing crashes can also be used for collisionavoidance pattern recognition as well as anticipatory sensing.

If a camera-based system is used for anticipatory sensing, an accurateimage can be obtained of the bullet object and a neural network-basedclassifier can identify what the object is. Unless stereo or other 3Dcamera systems are used, it is difficult to obtain the velocity andrange on the bullet object from the camera image alone unless rangegating is used as disclosed in U.S. patent application Ser. No.11/034,325. On the other hand, if a scanning laser ranging system isused, the image quality is poor if a single scan line is used andimproves with more scan lines but at the expense of increasing cost andcomplexity. A 6 sided polygon-based rotating mirror scanner can provide6 lines of scan and cover 60 degrees which is sufficient for frontal orrear impacts but probably not for side impacts where at least a 90degree or 120 degree scan is preferred. Fortunately, a neural networkcan usually accurately identify an object from a few scan linesespecially considering that the relative motion of the vehicle permitsthe system to really obtain more lines that the scanner produces in asingle revolution. An alternate system is to use a modulated laser orother light source in a diverging beam mode and to either modulate thelight and determine the nearest object and assume that it is areflection from the bullet object or to use a Kerr or Pokel cell orequivalent as a range gating light valve to permit an image of thebullet object to be acquired along with its range. In the latter case,the Doppler shift can be used to determine the velocity of the bulletobject (see the '325 application).

FIG. 19 is a front view of an automobile showing the location of anelectromagnetic wave anticipatory or collision avoidance sensor 145which can use the same neural computer system as the crash sensordiscussed above and thus is coupled thereto. Previously, radar and laserradar systems have been developed for collision avoidance systems. It isnoteworthy that no such systems have been fielded on a productionvehicle due to significant problems that remain to be solved. Analternate technology uses infrared electromagnetic waves and a receiverand processing system which both analyzes the image prior toillumination from the vehicle and after illumination to achieve moreinformation. The image is then digitized and fed into a neural networkfor analysis.

Once an anticipatory sensor is in place, the data can also be combinedwith data from acceleration sensors and occupant sensors fed into theneural network system for the smart airbag. Even prior to the smartairbag system, pre-crash data can be combined with acceleration data andthe acceleration data used to confirm the conclusions of the pre-crashsensor(s) with regard to mass of the striking object and the location ofthe impact. Thus, the data from the anticipatory sensor can beincorporated as soon as it is available to improve the airbag system.

As mentioned elsewhere herein and in other patents of the currentassignee, anticipatory sensors can also be used to identify the objectthat may be involved in a rear impact. In this manner, the driver wouldknow if he or she is about to run over something as the vehicle is beingoperated in reverse and also what the object is. Thus, an image of thatobject can be made available on any convenient display, such as aheads-up display to the vehicle operator. This provides a clear view ofobjects in the rear of the vehicle that may sometimes be difficult tosee in a video image. Anticipatory sensors are useful when a vehicle isabout to be impacted from the rear by another vehicle. Both the identityand the velocity can be determined and the seatbelts pretensioned, seatsand headrests adjusted etc. to prepare the occupant(s) for the impact.

Anticipatory sensors are most applicable for side impacts as discussedabove but of course can be effectively used for frontal and rearimpacts. Another feature that becomes available is the possibility ofusing the seatbelt or another small, positioning airbag that would beinflated prior to the curtain airbag to prevent the head of the occupantfrom being trapped between the window frame and the curtain airbag. Ifan IMU, or equivalent sensor system, is available, then the motion of anoccupant's head can be projected and again action taken to prevent headentrapment. If occupant sensors are also present that can visually orultrasonically, for example, track the occupant's head then, coupledwith appropriate acceleration sensors, the curtain airbag deploymenttiming can be made such that the occupant's head is not trapped. Asmentioned above, a seatbelt pretensioner can also be designed to providea force on the occupant to prevent entrapment.

Appendix 2 contains a technical report of frontal anticipatory sensingdevelopment.

1.7 Rollover Sensing

As mentioned above (see FIG. 2 and the tri-axial accelerometer and/orgyroscopes 56 (or IMU)), the event of a vehicle rollover can be sensedand forecasted early in the process through the use of the satelliteaccelerometers and/or the use of gyroscopes and in particular an IMU.

Additionally, if a plurality of GPS antennas are mounted spread apart onthe vehicle the vehicle attitude can be determined from the phases ofthe carrier signals from the GPS satellites. Outputs from these sensorscan be fed into a microprocessor where either a deterministic algorithmbased on the equations of motion of the vehicle or a pattern recognitionalgorithm can be used to process the data and predict the probability ofrollover of the vehicle. This process can be made more accurate if mapinformation is available indicating the shape of the roadway on whichthe vehicle is traveling. Furthermore, vertical accelerometers canprovide information as to inertial properties of the vehicle which canbe particularly important for trucks where the loading can vary.

1.8 Rear Impact Sensing

A preferred method for rear impact sensing as discussed herein is to useanticipatory sensors such as ultrasonic backup sensors. However, sensorsthat measure the crash after the crash has begun can also be used asalso disclosed herein. These can include the rod-in-tube crush sensor orother crush measuring sensors, a ball-in-tube velocity change sensor orother velocity change sensors, a swinging flapper inertially dampedsensor, an electronic sensor based on accelerometers or any otherprinciples or any other crash sensor. The sensor can be mounted in thecrush zone or out of the crush zone in the passenger compartment, forexample. A preferred non-crush zone mounted sensor is to use an IMU asdiscussed herein.

1.9 Sensor Combinations

If the passenger compartment discriminating sensor is of the electronictype, the triggering threshold can be changed based on the crushvelocity as measured by the sensor of this invention in the crush zone.Passenger compartment sensors sometimes trigger late on soft longduration frontal crashes even though the velocity change issignificantly higher than the desired deployment threshold (see, e.g.,reference 4). In such a case, the fact that the crush velocity sensorhas determined that a crash velocity requiring an airbag is occurringcan be used to modify the velocity change required for the electronicpassenger compartment-mounted sensor to trigger. Thus, in one case, thepassenger compartment sensor can prevent the deployment of the air bagwhen the velocity change is too low as in the animal impact situationdiscussed above and in the second case, the crush zone sensor can causethe discriminating sensor to trigger faster in a soft crash and minimizethe chance of a late triggering condition where the occupant isout-of-position and in danger of being injured by the deploying air bag.

FIG. 20 shows schematically such a circuit applied to side impacts wherean electronic sensor 159 triggers deployment of the side airbag residentin a side airbag module and crush velocity sensor 158 is used as inputto the electronic sensor 159. The electronic sensor could be mounted inthe passenger compartment but designed with a very low threshold. Itspurpose is to verify that a crash is in progress to guard against ahammer blow to the sensor setting off the airbag. In this case, thecurrent carrying capacity of the crush sensor 158 can be much less andthinner wires can be used to connect it to the electronic sensor 159.

In one scenario, the electronic sensor may be monitoring an event inprogress when suddenly the crush sensor 158 signals that the vehicle hascrushed with a high velocity where the sensor is mounted. The electronicsensor 159 now uses this information along with the acceleration signalthat it has been monitoring to determine the severity of the crash. Thecrush velocity sensor 158 informs the electronic sensor 159 that a crashof a certain velocity is in progress and the electronic sensor 159,which may comprise an accelerometer and a microprocessor with a crashanalysis algorithm, determines the severity of the crash based on theacceleration signal and the crush velocity.

If the acceleration signal is present but the crush sensor 158 fails torecord that a crash is in progress, then the electronic sensor 159 knowsthat the acceleration signal is from either a non-crash event or from acrash to some part of the vehicle, such as in front of the A-pillar orbehind the C-pillar where deployment of the airbag is not warranted. TheA-pillar is the forwardmost roof support member on which the front doorsare hinged and the C-pillar is the rearmost roof support pillar usuallyat or behind the rear seat.

Knowledge of the impact location, as detected using the coaxial cablesensor described above, can be used to alter the interpretation of theacceleration signal provided by the passenger compartment sensor, ifsuch is deemed beneficial. This may provide an advantage in that adecision to deploy an occupant restraint device is made earlier thannormally would be the case if the location of the impact location werenot considered in the control of the occupant restraint devices.

If the passenger compartment discriminating sensor is of the electronictype, the triggering threshold can be changed based on the condition ofthe sensor in the crush zone. Passenger compartment sensors sometimestrigger late on soft long duration crashes even though the velocitychange is significantly higher than the desired deployment threshold.See for example, SAE Paper No. 900548 (reference 4). In such a case, thefact that the crush velocity change sensor in the crush zone indicatesthat deployment of an airbag is required can be used to modify thevelocity change, or other parameters, required for the electronic sensorin the passenger compartment to trigger. Thus, in one case, thepassenger compartment sensor can prevent the deployment of the airbagwhen the velocity change is too low as in the animal impact and in thesecond case, the crush zone sensor can cause the passenger compartmentsensor to trigger faster in a soft crash and minimize the chance of alate triggering condition where the occupant is out-of-position and indanger of being injured by the deploying airbag.

FIG. 21 shows schematically such a circuit where an electronic sensor161 triggers deployment of the airbag and crush zone velocity sensor 160is used as input to the electronic sensor 161. In this case, the currentcarrying capacity of the crush zone sensor 160 can be much less andthinner wires can be used to connect it to the electronic sensor 161. Inone scenario, the electronic sensor 161 may be monitoring a crash inprogress when suddenly the front crush zone sensor 160 signals that thevehicle crush zone is experiencing a high velocity change. Theelectronic sensor 161 now realizes that this is a soft, deep penetrationcrash that requires an airbag according to a modified algorithm. Theconditions for deploying the airbag can be modified based on this crushvelocity information. In this manner, the combined system can be muchsmarter than either sensor acting alone. A low speed offset pole orcar-to-car underride crash are common real world examples where theelectronic sensor 161 in the passenger compartment might trigger latewithout the information provided by the forward-mounted crush zonesensor 160.

The crush zone sensor 160 can detect a reaction of the crush zone to thecrash, e.g., crush of the crush zone, a velocity change of the crushzone or acceleration of the crush zone. That is, sensor 160 does notnecessarily have to be one of the crush sensors disclosed above (oranother sensor which triggers based on crush of the crush zone of thevehicle) but rather, can be designed to trigger based on other reactionsof the crush zone to a crash, including the velocity change of the crushzone and the acceleration of the crush zone, as well as functionsthereof (and combinations of any such reactions).

FIG. 21A shows a schematic circuit of an arrangement in accordance withthe invention with a ball-in-tube sensor 162 as the crush zone sensorand FIG. 21B shows a schematic circuit of an arrangement in accordancewith the invention with an electronic sensor 163 as the crush zonesensor

Referring now to FIGS. 21C and 21D, in keeping with the same themediscussed with reference to FIGS. 21, 21A and 21B, an electronic crashsensor arrangement in accordance with the invention may include a firstelectronic crash sensor 164 mounted in the crush zone and a secondelectronic crash sensor 165 mounted outside of the crush zone, forexample in or around the passenger compartment. It may optionallyinclude one or more anticipatory sensors 166. A processor 167 is coupledto the crash sensors 164,165 to receive signals therefrom indicative ofmeasurements obtained by the crash sensors 164, 165. One or moreoccupant restraint devices 168 is coupled to the processor 167 andcontrolled thereby. The crash sensors 164, 165 are thus coupled togetherindirectly via the processor 167 or may be coupled together directly,i.e., via a common bus.

Each crash sensor 164, 165 provides measurements or data readings to theprocessor 167 which then determines whether the conditions for deployingany of the occupant restraint devices 168 are satisfied and if so,initiates deployment of one or more of the occupant restraint devices168. The conditions for deployment may be satisfied by the measurementsfrom only one crash sensor, e.g., a high velocity crash with onlyminimal crush of the vehicle or a low velocity crash with significantcrush of the vehicle, or from both crash sensors (or all three crashsensors when an anticipatory crash sensor 166 is provided or two of thethree crash sensors when an anticipatory crash sensor 166 is provided).

In addition, it is possible to relate the deployment conditions of thenon-crush-zone mounted sensor 165 to the measurements from the crushzone. In such an embodiment, the reaction of the crush zone to a crashis measured via the electronic crash sensor 164 (step 169 in FIG. 21D)and another reaction of the vehicle to a crash, other than crush, ismeasured by the second electronic crash sensor 165 (step 170). Themeasurements may be spaced in time or simultaneous. Thereafter, at step171, a determination is made, e.g., by processor 167, whether there is areaction in the crush zone, i.e., crush of the vehicle or a portionthereof. If so, an algorithm or parameters of the deployment may bemodified at step 172. Thereafter, a determination is made by theprocessor 167 whether any of the conditions for, deployment of theoccupant restraint device 168 are satisfied (step 173), either thepredetermined conditions or modified conditions.

If so, a control signal is generated and sent to deploy one or more ofthe occupant restraint devices to initiate deployment of the same (step174). If not, then the crash sensors 164, 165 would continue to measurethe reaction of the vehicle or portions thereof, i.e., a feedback loopto steps 169 and 170.

Thus, disclosed above is a crash sensor arrangement for determiningwhether the crash involving the vehicle requires deployment of theoccupant restraint device which comprises a first discriminating crashsensor mounted in a crush zone of the vehicle and structured andarranged to measure a reaction of the crush zone to the crash and asecond discriminating crash sensor mounted outside of the crush zone ofthe vehicle and structured and arranged to trigger by means other thancrush of the crush zone of the vehicle, e.g., based on acceleration or achange in velocity of the entire vehicle or a part thereof. Some typicalreactions of the crush zone which are measured by the firstdiscriminating crash sensor are the crush of the vehicle crush zone,acceleration of the vehicle crush zone, or velocity change of thevehicle crush zone. The first and second discriminating sensors arecoupled to one another such that a signal to deploy the occupantrestraint device may be generated in consideration of the first sensormeasurements and whether the second sensor has triggered. Thus, incertain crashes, the occupant restraint device will not deploy unlessboth sensors have been triggered, i.e., the conditions imposed on eachcrash sensor for deploying the occupant restraint device have beensatisfied.

In one embodiment, the sensors are coupled to one another in series suchthat the signal to deploy the occupant restraint device is generatedonly when the first and second sensors are both triggered. In anotherembodiment, the second sensor receives a signal indicative of triggeringof the first sensor, considers whether to modify its triggeringalgorithm, triggering criteria and/or sensitivity based on thetriggering or velocity change of the first sensor and if so, modifiesthe triggering algorithm, criteria or sensitivity. If the second sensoris an electronic sensor arranged to trigger based on a change invelocity and/or acceleration of the vehicle (or functions thereof), thevelocity change and/or acceleration (or functions thereof) required fortriggering may be modified based on the triggering of the first sensor.Such modification is not required in the event the velocity change isalready appropriate.

The first discriminating sensor mounted in the crush zone may be a tapecrush sensor including a tape switch comprising a pair of electricallyconductive members spaced apart from one another prior to crush of thevehicle and which are designed to come into contact with one anotherupon crush of the vehicle of a specific magnitude. The tape crush sensorcan include a mechanism for reducing the sensitivity of the tape crushsensor, such as an encapsulating member around the sensor. The firstdiscriminating sensor may also be a ball-in-tube sensor or an electronicsensor.

Another embodiment disclosed above of a crash sensor arrangement fordetermining whether the crash involving the vehicle requires deploymentof the occupant restraint device comprises a first discriminating crashsensor mounted outside of the crush zone of the vehicle and structuredand arranged to trigger by means other than crush of the crush zone ofthe vehicle, and a second discriminating crash sensor coupled to thefirst sensor and mounted in the crush zone of the vehicle, e.g., a tapecrush sensor or an electronic sensor. The second sensor providesinformation about a reaction of the crush zone of the vehicle to thecrash, e.g., information about crush, velocity or acceleration of thevehicle crush zone, to the first sensor such that the first sensor mayaffect and modify its triggering and/or sensitivity based on theinformation about crush, velocity or acceleration of the vehicle crushzone provided by the second sensor, if such modification is necessary.

The method for determining whether the crash involving the vehiclerequires deployment of an occupant restraint device comprises mounting afirst crash sensor in the crush zone of the vehicle, e.g., a tape crushor coaxial cable sensor or an electronic crash sensor, and which istriggered based on a reaction of the crush zone to the crash (e.g.,crush, velocity change or acceleration, or a function thereof, of thevehicle crush zone), mounting a second crash sensor outside of the crushzone of the vehicle and which is triggered by means other than crush ofthe crush zone of the vehicle, and deploying the occupant restraintdevice in consideration of whether the first sensor has triggered andwhether the second sensor has triggered. If the first and second sensorsare coupled to one another in series, the occupant restraint device maybe deployed only when the first and second sensors are both triggered(for certain types of crashes). In the alternative, a signal indicativeof measurements made by the first sensor is directed to the secondsensor and consideration is made as to whether the conditions fortriggering of the second sensor should be affected and modified based onthe measurements of the first sensor. If so, the triggering conditionsare modified.

In another method disclosed above for determining whether a crashinvolving a vehicle requires deployment of an occupant restraint device,a first discriminating crash sensor is mounted outside of the crush zoneof the vehicle and is triggered to deploy the occupant restraint deviceby means other than crush of the crush zone of the vehicle, and a seconddiscriminating crash sensor is mounted in the crush zone of the vehiclesuch that the second sensor generates information about a reaction ofthe crush zone to the crash. As above, such reactions may be typicallythe crush, velocity change or acceleration of the vehicle crush zone.The second sensor may be a tape, rod-in-tube or coaxial cable crushsensor which provides information about the velocity change the crush ofthe vehicle at the mounting location of the sensor or it may be anelectronic sensor that uses the acceleration in the crush zone todetermine sensor triggering or transmits the acceleration signal to theprocessor which then considers both acceleration signals from the crushzone and the non-crush zone mounted sensors.

The information about the reaction of the crush zone of the vehicle tothe crash is provided by the second sensor to the first sensor anddeployment of the occupant restraint device is controlled via the firstsensor based on the information about the reaction of the crush zone ofthe vehicle to the crash provided by the second sensor.

In some cases, when the non-crush zone sensor is not present ormalfunctioning, or when there is an insufficient signal at the non crushzone sensor mounting location, the processor may initiate triggeringbased on the acceleration signal of the crush zone mounted accelerometeralone.

In another embodiment of the invention disclosed above, a vehicle crashsensor system comprises a crush velocity detecting sensor changeablefrom an open position indicative of a non-crush situation toward aclosed position indicative of crush of a portion of the vehicleproximate to the sensor, an electronic sensor coupled to the crushvelocity detecting sensor and comprising an accelerometer, and meanscoupled to the accelerometer for initiating deployment of the occupantprotection device based on velocity of the crush velocity detectingsensor and an analysis of output from the accelerometer indicative of asituation in which deployment of the occupant protection device isdesired. A mechanism is provided for retaining the crush velocitydetecting sensor in the closed position upon contact of the conductingmembers of the crush velocity detecting sensor from the open position tothe closed position. The crush detecting switch may be mounted on a sideof the vehicle so as to detect crush of the side of the vehicle.

FIG. 70 illustrates the placement of a variety of sensors, primarilyaccelerometers and/or gyroscopes, which can be used to diagnose thestate of the vehicle itself. Sensor 571 can measure the acceleration ofthe firewall or instrument panel and is located thereon generally midwaybetween the two sides of the vehicle. Sensor 572 can be located in theheadliner or attached to the vehicle roof above the side door.Typically, there will be two such sensors one on either side of thevehicle. Sensor 573 is shown in a typical mounting location midwaybetween the sides of the vehicle attached to or near the vehicle roofabove the rear window. Sensor 576 is shown in a typical mountinglocation in the vehicle trunk adjacent the rear of the vehicle. One, twoor three such sensors can be used depending on the application. If threesuch sensors are use one would be adjacent each side of vehicle and onein the center. Sensor 574 is shown in a typical mounting location in thevehicle door and sensor 575 is shown in a typical mounting location onthe sill or floor below the door. Finally, sensor 577, which can be alsomultiple sensors, is shown in a typical mounting location forward in thecrush zone of the vehicle. If three such sensors are used, one would beadjacent each vehicle side and one in the center.

In general, sensors 571-577 measure a physical property of the locationat which they are mounted. For example, the physical property would bethe acceleration of the mounting location if the sensor is anaccelerometer and would be angular inclination if the sensor is agyroscope. Another way of looking at would be to consider that sensors571-577 provide a measurement of the state of the sensor, such as itsvelocity, acceleration, angular orientation or temperature, or a stateof the location at which the sensor is mounted. Thus, measurementsrelated to the state of the sensor would include measurements of theacceleration of the sensor, measurements of the temperature of themounting location as well as changes in the state of the sensor andrates of changes of the state of the sensor. However, any described useor function of the sensors 571-577 above is merely exemplary and is notintended to limit the form of the sensor or its function.

Each of the sensors 571-577 may be single axis, double axis or triaxialaccelerometers and/or gyroscopes typically of the MEMS type. Thesesensors 571-577 can either be wired to the central control module orprocessor directly wherein they would receive power and transmitinformation, or they could be connected onto the vehicle bus or, in somecases, using RFID technology, the sensors can be wireless and wouldreceive their power through RF from one or more interrogators located inthe vehicle. In this case, the interrogators can be connected either tothe vehicle bus or directly to control module. Alternately, an inductiveor capacitive power and information transfer system can be used.

One particular implementation will now be described. In this case, eachof the sensors 571-577 is a single or dual axis accelerometer. They aremade using silicon micromachined technology such as disclosed in U.S.Pat. Nos. 5,121,180 and 5,894,090. These are only representative patentsof these devices and there exist more than 100 other relevant U.S.patents describing this technology. Commercially available MEMSgyroscopes such as from Systron Doner have accuracies of approximatelyone degree per second. In contrast, optical gyroscopes typically haveaccuracies of approximately one degree per hour. Unfortunately, theoptical gyroscopes are prohibitively expensive for automotiveapplications. On the other hand, typical MEMS gyroscopes are notsufficiently accurate for many control applications.

The angular rate function can be obtained through placing accelerometersat two separated, non-co-located points in a vehicle and using thedifferential acceleration to obtain an indication of angular motion andangular acceleration. From the variety of accelerometers shown on FIG.70, it can be readily appreciated that not only will all accelerationsof key parts of the vehicle be determined, but the pitch, yaw and rollangular rates can also be determined based on the accuracy of theaccelerometers. By this method, low cost systems can be developed which,although not as accurate as the optical gyroscopes, are considerablymore accurate than conventional MEMS gyroscopes.

Instead of using two accelerometers at separate locations on thevehicle, a single conformal MEMS-IDT gyroscope may be used. Such aconformal MEMS-IDT gyroscope is described in a paper by V. K. Varadan,“Conformal MEMS-IDT Gyroscopes and Their Comparison With Fiber OpticGyro”. The MEMS-IDT gyroscope is based on the principle of surfaceacoustic wave (SAW) standing waves on a piezoelectric substrate. Asurface acoustic wave resonator is used to create standing waves insidea cavity and the particles at the anti-nodes of the standing wavesexperience large amplitude of vibrations, which serves as the referencevibrating motion for the gyroscope. Arrays of metallic dots arepositioned at the anti-node locations so that the effect of Coriolisforce due to rotation will acoustically amplify the magnitude of thewaves. Unlike other MEMS gyroscopes, the MEMS-IDT gyroscope has a planarconfiguration with no suspended resonating mechanical structures.

Accelerometers and gyroscopes based on SAWs have been reported in theliterature mentioned herein. Some such SAW devices can be interrogatedwirelessly and require no source of power other than the received RFfrequency. Such devices, therefore, can be placed in a variety oflocations within or on a vehicle and through a proper interrogator canbe wirelessly interrogated to obtain acceleration and angular rateinformation from various locations. For example, a plurality of suchdevices can be distributed around the periphery of a vehicle to sensethe deformation velocity or angular rate of a portion of the peripheryof the vehicle giving an early crash signal.

The system of FIG. 70 using dual axis accelerometers therefore providesa complete diagnostic system of the vehicle itself and its dynamicmotion. Such a system is far more accurate than any system currentlyavailable in the automotive market. This system provides very accuratecrash discrimination since the exact location of the crash can bedetermined and, coupled with knowledge of the force deflectioncharacteristics of the vehicle at the accident impact site, an accuratedetermination of the crash severity and thus the need for occupantrestraint deployment can be made. Similarly, the tendency of a vehicleto roll over can be predicted in advance and signals sent to the vehiclesteering, braking and throttle systems to attempt to ameliorate therollover situation or prevent it. In the event that it cannot beprevented, the deployment side curtain airbags can be initiated in atimely manner.

Similarly, the tendency of the vehicle to the slide or skid can beconsiderably more accurately determined and again the steering, brakingand throttle systems commanded to minimize the unstable vehiclebehavior.

Thus, through the sample deployment of inexpensive accelerometers andMEMS gyroscopes, particularly MEMS-IDT gyroscopes, at a variety oflocations in the vehicle, significant improvements are made in thevehicle stability control, crash sensing, rollover sensing, andresulting occupant protection technologies.

Finally, as mentioned above, the combination of the outputs from theseaccelerometer sensors and the output of strain gage weight sensors in avehicle seat, or in or on a support structure of the seat, can be usedto make an accurate assessment of the occupancy of the seat anddifferentiate between animate and inanimate occupants as well asdetermining where in the seat the occupants are sitting. This can bedone by observing the acceleration signals from the sensors of FIG. 70and simultaneously the dynamic strain gage measurements from theseat-mounted strain gages. The accelerometers provide the input functionto the seat and the strain gages measure the reaction of the occupyingitem to the vehicle acceleration and thereby provide a method ofdetermining dynamically the mass and other inertial properties of theoccupying item and its location. This is particularly important duringoccupant position sensing during a crash event. By combining the outputsof the accelerometers and the strain gages and appropriately processingthe same, the mass and weight of an object occupying the seat can bedetermined as well as the gross motion of such an object so that anassessment can be made as to whether the object is a life form such as ahuman being.

For this embodiment, sensor 578 represents one or more strain gageweight sensors mounted on the seat or in connection with the seat or itssupport structure. Suitable mounting locations and forms of weightsensors are discussed in the current assignee's U.S. Pat. No. 6,242,701and contemplated for use in this invention as well. The mass or weightof the occupying item of the seat can thus be measured based on thedynamic measurement of the strain gages with optional consideration ofthe measurements of accelerometers on the vehicle, which are representedby any of sensors 571-577.

1.10 Safety Bus

The vehicle safety bus is described in U.S. Pat. Nos. 6,533,316 and6,733,036 and can be used with any or all of the sensors, sensorsystems, airbag systems and safety systems disclosed herein.

2 Inflators

2.1 Elongate Airbag Module

2.1.1 Ceiling-Mounted

An airbag module constructed in accordance with the teachings of theinvention and adapted for mounting, e.g., on a ceiling 431 in apassenger compartment 459 of a motor vehicle to protect rear seatoccupants in collisions and particularly frontal collisions, is showngenerally at 430 in FIG. 52. Airbag module 430 is elongate and includesan inflator module 439 and an airbag 433 (which may be madesubstantially of plastic film but could also be made of other material)which is coupled to the inflator module 439. Airbag module 430 isattached to a mounting surface of the vehicle which, in the illustratedembodiment, is a middle region of the ceiling 431 by fastening members432. The airbag module 430, or at least the airbag 433 housed therein,is dimensioned so that it extends across substantially the entiredistance between the side windows. Airbag module 430, and moreparticularly the inflator module 439, is also coupled to a sensor anddiagnostic module 458 which receives input data and determines if anaccident involving the vehicle is of such severity as to requiredeployment of the airbag 433. If so, the sensor and diagnostic module458 sends a signal to the inflator module 439 to start the process ofdeploying the airbag, i.e., by initiating the burning of a propellanthoused within a gas generator portion of the inflator module 439 asdescribed in more detail below. Airbag module 430 may also be attachedto the ceiling of the vehicle in a position to deploy the airbag betweenthe dashboard and any front-seated occupants.

FIG. 53A is a cross-sectional view of the airbag module 430 prior toinflation of the airbag 433. As shown in FIG. 53A, the airbag module 430includes a protective cover 452 which partially defines a housing of theairbag module 430 and as such, encloses the airbag 433 and an interiorportion of the airbag module 430 and prevents contaminated particlesfrom entering the interior of the airbag module 430. Shortly after theinflator module 439 is directed to initiate burning of the propellant,the protective cover 452 is released as a direct result of the burningpropellant and the folded airbag 433 begins to inflate using acombination of gases from both the gas generator portion of the inflatormodule 439 and, through aspiration, from the passenger compartment 459of the vehicle.

The term “airbag” as used herein means either the case where the airbagmodule 430 contains a single airbag, as in most conventional designs, orwhere the airbag module 430 contains a plurality of airbags, possiblyone inside another or several airbags inside a limiting net having asmaller volume than the volume of the airbags (see U.S. Pat. Nos.5,505,485 and 5,653,464), or where the airbag module 430 contains asingle airbag having a plurality of compartments which deploy in concertto protect an occupant. The term “inflator” as used herein means the gasgenerator plus all other parts required to deliver gas to the airbagincluding the aspiration system if present. The term “gas generator”, onthe other hand, refers only to the propellant, its housing and all otherparts required to generate gas. In non-aspirated implementations, theinflator and the gas generator are the same. The terms “propellant” and“gas generator” are used sometimes herein as equivalents. The term“cover” as used herein means any type of covering for enclosing aninterior portion of the airbag module 430, or at least for overlying theairbag 433 per se, to protect the same and may even constitute a simplecovering on an outermost region of the airbag 433. Thus, it will beappreciated by those skilled in the art that the cover may be thematerial which forms the outer peripheral surface of the passengercompartment, e.g., fabric, without deviating from the objects of theinvention. Alternatively, the covering may actually be a surface of theairbag itself coated to appear like a cover.

FIG. 53B is a view of the airbag module 430 of FIG. 53A after theinitial stage of airbag inflation where the initial gas from the gasgenerator has generated sufficient pressure within the interior of theairbag module 430 to force the release of the cover 452. FIG. 53C showsthe airbag 433 in its inflated condition and is a view taken along lines53C-53C of FIG. 52. The cover 452 may also be released by other meanssuch as a pyrotechnic system.

In the embodiment illustrated in FIGS. 53A, 53B and 53C, airbag module430 is substantially elongate and inflator module 439 comprises anelongate gas generator made from an approximatelyrectangular-cross-section housing, such as a tube 440, with at least oneopening 441 therein for outflow of gas generated thereby. Tube 440 hasan arcuate, longitudinally extending bottom wall 448, adjoininglongitudinally extending side wall, lateral end walls and a top wall(more clearly visible in FIG. 531) which together define a reactionchamber.

A propellant 444 in the form of an elongate block of solid material isaffixed to the inner surface of the walls of tube 440 in a significantportion of the interior of tube 440. The block of propellant 444completely overlies the bottom wall 448 and rises along the side andlateral end walls but does not reach the top of these walls as shown inFIG. 53A. Thus, not all of the reaction chamber is filled withpropellant 444. The propellant 444 is thus arranged along substantiallythe entire length of the bottom wall 448 and side walls.

The surface of the propellant 444 not engaging or in contact with a wallof the tube 440 is preferably coated with a layer of pyrotechnic ignitermix 445 such as a coating made from nitrocellulose and BKNO3, or othersuitable materials, to aid in starting burning of the propellant 444. Inthese embodiments, the propellant is entirely enclosed by the walls ofthe tube 440 and the layer or coating of the igniter mix 445. This layerof igniter mix 445 also serves to seal the propellant 444 from theenvironment, i.e., the atmosphere. If the material of the igniter mix445 is made at least partially from nitrocellulose or anotherappropriate sealant, then another seal to isolate the propellant 444from the atmosphere is not required and the propellant 444 iseffectively hermetically sealed.

A screen member 446 is also positioned within tube 440 in a positionspaced from the layer of igniter mix 445 covering the propellant 444 andadjacent to the opening(s) 441 to prevent any particulate matter fromleaving the tube 440. Opening 441 is situated in a top wall of the tube440 opposite the bottom wall 448. A chamber 442 is thus defined betweenthe screen member 446 and the layer of igniter mix 445, which chamber442 is only a portion of the entire reaction chamber defined by thewalls of the tube 440. Although any screen member 446 will inherentlyprovide some initial cooling of the gas from the propellant 444, this issimply an ancillary benefit. On the other hand, for cases where theselected propellant 444 is known to burn at too high a temperature, thescreen member 446 can be made thicker so as to also serve as a heatsink, i.e., its size can be regulated to affect the temperature of thegases generated by the burning propellant 444 and expelled from the gasgenerator 439.

Upon receiving a signal from the sensor and diagnostic module 458, anelectronic module (not shown) ignites a squib at one end of the inflatormodule 433 (FIG. 52) which ignites the igniter mix 445 which in turnignites the propellant 444. The propellant 444 burns in a direction fromthe surfaces coated by the igniter mix 445 toward wall 448 (FIG. 53A),which is opposed to the wall of the tube 440 having the opening(s) 441until the propellant 444 is totally consumed. It will be appreciated bythose skilled in the art that the size of the tube 440 can be regulated,i.e., elongated or widened, depending on the propellant used and ideallyminimized based on appropriate selection of the propellant and therequired gas output parameters of the gas generator, without deviatingfrom the scope of the invention.

It will also be appreciated by those skilled in the art that the ignitermix 445 is substantially coextensive with the propellant 444 in alongitudinal direction, i.e., exposed portions of the propellant 444 arecovered by the igniter mix 445 so that they are inherently coextensive.As such, upon ignition of the igniter mix 445, the propellant 444 beginsto burn across its entire length. This is beneficial as the pressuregenerated by the gas may be substantially uniform provided thepropellant 444 is uniformly distributed and homogeneous. Othergeometries for the igniter mix are possible without deviating from theinvention.

The airbag module 430 can also include, external of the tube 440 and influid communication with the opening(s) 441, a mixing chamber 447 inwhich the gas from the gas generator 439 resulting from burning of thepropellant 444 and gas from the passenger compartment 459, e.g., air,entering through an aspiration nozzle or inlet ports or inlet slits 450are combined, and from which the combined gases are delivered to theairbag 433 through a port or nozzle, i.e., converging-diverging nozzle435 (FIGS. 53B and 53C).

The airbag module 430 also comprises elongate U-shaped nozzle walls 456(which define the nozzle 435 therebetween), a base 434 which is mountedto the ceiling 431, or other mounting surface, by the fastening members432 (FIG. 52) and support springs 451. The gas generator 439 is attachedto base 434 by brackets 457 described in more detail below (FIG. 53F).Each of the nozzle walls 456 has two leg portions 456 a 1, 456 a 2extending from opposite end regions of a base portion 1456 b. At leastone of the springs 451, two in the illustrated embodiment, is attachedto leg portion 456 a 1 of each nozzle wall 456 and, as shown in FIG.53A, prior to airbag inflation they are maintained in a compressed stateso that the walls 456 are proximate to the base 434, i.e., theaspiration inlet ports 450 are substantially closed. Attached to thebase portion 456 b of each nozzle wall 456 is a spring shield 455 whichsupports and protects the material of the airbag 433 during the initialinflation period, as shown in FIG. 53B, prior to the start of theaspiration when the gases are hot, keeping the airbag 433 from blockingthe inlet to the inflator module 439 from the passenger compartment 459.Prior to inflation of the airbag 433, the spring shields 455 exertpressure against the folded airbag 433 to force the same against thecover 452. During inflation, the spring shields 455 are designed to beforced outward by the expulsion of gases from the gas generator 439 andhelp start the airbag deployment process since the cover 452 no longeracts to restrain the airbag 430, and then the support shields 455 formthe converging and diverging portions of the low pressure part of theaspiration nozzle 435. Ends of the airbag 433 are connected to legportions 456 a 2. This process uses the high pressure gas from theinflator to initiate deployment of the airbag prior to the start of theaspiration process. In this manner, the initial force needed to releasethe cover and start the airbag deployment is provided by the initialburning of the propellant. In some cases, two propellant formulationsare used. A first rapidly burning mixture to provide an initial highpressure for cover release and initial deployment, followed by a slowerburning propellant for inflating the airbag with aspirated air.

In view of this construction, the airbag 433 is not circular but ratheris elongate as shown in FIG. 52. Some of the advantages of thisnon-circular airbag 433 are its ease of manufacture from flat plasticfilm sheets as described in U.S. Pat. No. 5,653,464 and its ease inparallel folding the airbag into the module 430. In this regard, in viewof the elongated shape of the airbag 433, it can be folded lengthwise inthe airbag module 430.

In operation, shortly after the propellant 444 has been ignited by theigniter mix 445 and the cover 452 has been released, high pressure gasbegins to flow through screen 446, through opening(s) 441 and outthrough a converging-diverging nozzle 436, 437, 438, also referred to asa convergent-divergent nozzle. The nozzle 436, 437, 438 extends alongthe longitudinal sides of the inflator module 439. This nozzle has theeffect of causing a jet of the combustion gases to achieve a highsupersonic velocity and low pressure and to spread to rapidly fill themixing chamber 447 formed by an outer wall of tube 440, nozzle walls 456and spring shields 455. This causes a low pressure to occur in themixing chamber 447 causing substantial amounts of gas to flow throughaspirator inlet ports 450, which are opened by the expansion of springs451 forcing nozzle walls 456 to move away from base 434 as shown, e.g.,in FIGS. 53B and 53C. The converging portion 436 of the nozzle isconstructed so that its cross-sectional area gradually decreases untilthroat 437. After throat 437, the cross-sectional area of the divergingportion 438 of the nozzle gradually increases toward exit 449. Thus,after the throat 437, there is a significant continuation of the nozzleto provide for the diverging portion 438. An approximate analysis of anaspirating system similar to that of this invention appears in Appendix1.

The pressure then begins to build in the mixing chamber 447 untilsufficient pressure is obtained to finish expelling the cover 452causing springs 451 to expand even more, support shields 455 to beopened to fully open the nozzle 435 and airbag 433 to be furtherdeployed. Prior to release, the cover 452 is retained by a catch 453.Upon pressurization of the mixing chamber during airbag deployment, atab 454 on cover 452 is pulled from under catch 453 releasing the cover.Since the pressure builds at the end of the module which is initiallyignited by the squib, not shown, the tab 454 is initially released atthat end and then is rapidly pulled out from under catch 453 progressingto the end furthest away from the squib. This process can be facilitatedby removal of either the tab 454 or catch 453 at the squib end of theairbag module 430. In this manner, the cover 452 is easily released yetretains the airbag 433 during normal vehicle operation. One importantfeature of the invention is that since the flow out of the high-pressurenozzle is supersonic, the pressure rise needed to further expel thecover 452 will not affect the flow through the nozzle. This is true aslong as the flow remains supersonic which, in the preferred design, isset to permit a ten-fold pressure rise to expel the cover 452 over thatwhich should be required. Since relatively little pressure is requiredto expel the cover 452, if an object is loading the cover 452 in onelocation in the longitudinal direction of the tube 440, the pressurewill be released by flowing out to the sides of the obstruction, i.e.,at other longitudinal locations. This design is unique in that thepressure buildup never reaches the point that it will cause injury to anout-of-position occupant. Even if the entire cover 452 is restrained,which is virtually impossible, the cover 452 will release the gas to thesides.

Although the airbag 433 is stored in a compact arrangement as shown inFIG. 53A, when it deploys, the aspiration inlet ports 450 and theconverging-diverging nozzle 435 become quite large especially whencompared with the size of the high pressure nozzle 436, 437, 438. It isbecause of this geometry that very high aspiration pumping ratios areachievable in the invention compared to the prior art. Representativedimensions for the high-pressure nozzle are about 0.054 inches for theconverging portion 436 of the nozzle, about 0.0057 inches for theminimum opening or throat 437, to about 0.1 inches at the exit 449 ofthe nozzle in the diverging portion 438. Representative dimensions forthe aspirating nozzle on the other hand are about 1 inch at the inletports 450, about 2 inches at the minimum double clearance, i.e., theminimum distance between spring shields 455. The length of the mixingportion of the nozzle is about 2 inches for the illustrated design. Itis the ratio of the minimum high pressure gas jet thickness, here about0.0057 to the length on the mixing channel, here about 2 inches, whichis only made possible by the design disclosed herein where the gas jetis very long and thin. The dimensions provided here are illustrativeonly and the actual dimensions will vary according to the particularapplication and the particular gas generator used.

FIG. 53D shows the state of the airbag module 430 when the propellant444 has completed its burning cycle and the pressure has dropped in themodule 430 and the springs 451 are acting to move the walls 456 in adirection toward the base 434, i.e., toward their initial position inwhich the inlet port 450 are substantially closed. The springs 451 donot return the walls 456 completely to their initial position but rathermaintain a sufficient opening between base 434 and walls 456 to permitthe gases to vent from the airbag 433 as it is loaded by an occupant,i.e., so that gases will flow in an opposite direction through inletport 450 than the direction of gas flow during inflation of the airbag433. Springs 451 are typically made from flat strips of spring steel.

In the nozzle, the gas flow initially converges to a very thin crosssection that in one preferred design is about 0.005 inches. It thenexpands becoming supersonic and emerges from the high-pressure nozzle asa sheet canted or slanted at an angle with respect to the incomingaspirated air. As shown in FIG. 53C, the gas from the gas generator 439flows in a direction F2 whereas the gas from the passenger compartment459 flows from the aspirating inlet ports 450 in a direction F1 that isat an angle α to the direction F2. This interaction between the twoplanar flows at an angle promotes efficient mixing of the two gas flowsas the flow downstream and into the airbag. In most cases, the angles ofthe two flows can be adjusted in the design to assure this efficientmixing. In some cases, additional measures are implemented such asvarying the directions of the combined flows to further promote mixingbefore the gas mixture enters the airbag 433. The design illustrated inthe figures provides ample space for the gas flows to mix after theirinitial impact.

In accordance with the invention, the length of the gas generator 439 ismeasured in a horizontal or longitudinal direction perpendicular to thedirection of the flow of the gas and is the longest dimension of thedevice. The length of the nozzle 436, 437, 438, on the other hand, ismeasured in the direction of the gas flow and perpendicular to thelength of the gas generator 439. A distinctive feature of the inflatormodule of this invention is that its length is much longer that itswidth or thickness and the length of the mixing chamber is much longerthan the minimum thickness of the high pressure jet. It is this ratiowhich governs the completeness of the mixing of the gases generated bythe propellant 444 and the gases from the passenger compartment 459which in turn governs the pumping ratio and thereby permits the largepumping ratios achieved here in contrast to the constructions disclosedin prior art patents discussed above. This is achieved by using a verylong and thin jet of high pressure gas which is achieved by the elongateairbag module 430 disclosed herein. It is known in the art that thevolume of gas flowing from a gas generator is proportional to thecross-sectional area of the jet times its length, but the ability of thejet to mix rapidly with the aspirating air is determined by the surfacearea of the jet. By using the thin linear geometry disclosed herein, theratio of surface area to cross section area is maximized which in turnmaximizes the amount of air which can be pumped and thus the pumpingratio. Other geometries can achieve high pumping ratios only byincreasing the mixing length. In most implementations, however, this isnot practical since there is insufficient space in the vehicle. This isthe main reason that current inflators are limited to pumping ratios ofsubstantially less than 1:1. In the case described above, the ratio ofthe mixing length to the minimum jet diameter is greater than 200:1. Inmost cases, in the implementation of this invention this ratio willexceed 100:1 and in all cases 50:1. Similarly, the ratio of the lengthof the gas generator 439 to the minimum thickness of the gas jet in thecase described in FIG. 52 and FIGS. 53A-53F is greater than 4000:1. Inmost cases, this ratio will be greater than 1000:1 and preferably itwill be greater than 100:1.

Referring now to FIG. 53F, it can be seen that the nozzle walls 456 aresolid and extend in the longitudinal direction of the tube 440.Similarly, spring shields 455 are connected to the walls 456 oversubstantially the entire length of the walls 456. However, springs 451are thin members which are connected only at discrete locations to thewalls 456 such that upon release of the springs 451 during airbaginflation, gas from the passenger compartment 459 can flow around andbetween the springs 451 into the mixing chamber 447. Although twosprings 451 are shown, it is of course possible to have a single springor more than two springs. Further, it is important to note that thelength of the gas generator 439 does not have to be the same as thelength of the nozzle walls and the module 430.

Further, it is a known property or characteristic of propellants, e.g.,propellant 444 situated in the tube 440, that their burn rate isdependent on the surrounding pressure, in this case the pressure inchamber 442 in the tube 440. The gas flow rate out of chamber 442depends on the flow resistance through the opening(s) 441 and theclearance at the throat 437 between the outer wall of the tube 440 andthe base 434. In FIG. 53F, this clearance is nominally set by supportingbrackets 457 which are connected to the tube 440 at one end region andto the base 434 at an opposite end region. The brackets 457 are designedto hold the tube 440 at a certain distance from base 434. These brackets457 can be designed to operate in three different ways: (i) as a fixedsupport, (ii) as a flexible support, or (iii) as a support which changeswith temperature. In general, brackets 457 serve to fix the minimumclearance at throat 437 between the gas generator 439 as a unit and thesupport base 434.

If brackets 457 operate as fixed supports, then the inflator will have aresponse which varies with temperature as is the case with allconventional inflator designs. This greatly increases the total amountof propellant which is required as discussed below.

If support brackets 457 are made elastic or flexible, supports 443 arearranged in the converging portion 436 of the nozzle defined by the tube440 and the support base 434 (FIG. 53E). The brackets 457 thenspring-load the tube 440 against the supports 443 so that the tube 440can lift off of supports 443 when the pressure is sufficient to overcomethe spring force of supports which act in the compression direction tokeep tube 440 close to the base 434. In this case, the clearance atthroat 437 between the tube 440 and base 434 increases, which reducesthe flow restriction which in turn reduces the pressure within chamber442 resulting in a nearly constant propellant burn rate and thus aninflator which operates relatively independent of temperature. Thesupports 443 are in the form of projections which are arranged at aplurality of spaced apart discrete locations between the base 434 andthe gas generator tube 440 and fix the minimum clearance for the casewhere the support brackets 457 are elastic or flexible.

Alternately, the brackets 457 can be made from strips of bimetallicmaterial and, through a proper choice of materials and geometry, thebrackets 457 will deform over temperature to vary the clearance atthroat 437 also with the ambient temperature in order to increase theclearance at throat 437 with temperature thus reducing the flowresistance and reducing the pressure in chamber 442 with temperatureproviding partial compensation for the variation in the combustion rateof the gas generated as a function of temperature.

Although in the preferred implementations of the invention describedabove, the propellant is placed within the tube 440, in some cases it isdesirable to place the gas generator in another location and to use thetube geometry described above to distribute the gas to the high-pressurenozzle. Thus, it will be appreciated by those skilled in the art that itis not required to generate gas within the inflator housing tube per sebut it is possible to generate the gas in an auxiliary structure anddirect the generated gas into the tube which then merely distributes thegas. Such an embodiment is illustrated schematically in FIG. 53H wherean inflator 460 is illustrated in a position connected to tube 440 by aconduit through which gas generated in inflator 480 would be conductedinto the tube 440. The inflator 460 is shown here for illustrativepurposes only and is not meant to indicate the actual size or locationof the inflator. If a conventional inflator were used, it would beconsiderably larger than inflator 460. Such an inflator 460 could beplaced adjacent to, or in the vicinity of, the tube 440 or at a moreremote location with the gas being transmitted to tube 440 through anytype of conduit or tube. Such an arrangement is particularly useful whenthe selected propellant does not burn cleanly and the effluent must befiltered. Although the inflator now feeds gas to the tube from one end,the remainder of the operation of the module is the same as describedabove.

An alternate approach is illustrated in FIG. 124 which shown a sidecurtain airbag device 910 with an aspirated inflator 911 located on oneend in contrast to FIG. 53H where the aspiration takes place along theentire module. This aspirated inflator is designed as a pyrotechnic gasgenerator; however, a stored gas system is also quite viable. With anaspiration ratio of 5 (assignee's scientists have achieved aspirationratios of 7 experimentally and 10 theoretically—see Appendix 3) a 10liter bag would require about 200 ml of compressed gas stored at 20atmospheres assuming that a desired pressure in the airbag is about 2atmospheres absolute. A stored gas system of course has an advantage ofbeing clean and cool. A release system is known in the blow down windtunnel art whereby a small electric spark across a sectored plastic orcombined metal and plastic, for example, membrane instantly opens such astored gas container without producing shrapnel. The need for relativelycool gas for the side curtain airbag is well known since the airbagshould remain inflated for 5-7 seconds. Thus, even if a pyrotechnicinflator is used, an aspiration system will reduce the averagetemperature to meet this requirement. Thus both systems producerelatively cool gas in a very simple and effective manner requiringsubstantially less space and at a significant cost reduction.

An alternate version of the elongate inflator as disclosed herein foruse as a thin distributed aspirated inflator 913 for side curtainairbags 912 for mounting on the roof rail, for example, is illustratedin FIG. 125. In this case, the inflator can be made from either metal orplastic and can be manufactured by an extrusion process. In either case,the inflator is extremely flexible making it especially easy to conformto a curved mounting location such as the roof rail. The elongateaspirated inflator disclosed in FIGS. 53A-53I of course has thisflexibility property. A more recent patent, U.S. Pat. No. 6,755,438,also describes a flexible inflator but not based on aspirationprinciples.

A key advantage of the plastic or metal inflator shown in FIG. 125 isthat it lends itself to accommodate a variety of airbag system designsfor different vehicles. The inflator can be easily cut into any lengthto fit a particular vehicle model thus greatly reducing tooling costs.U.S. Pat. No. 6,595,546 attempts to accomplish this in a complicatedmanner through attaching modular inflators together.

The gas generator in an inflator burns for a few milliseconds and in anaspirated inflator the amount of propellant required is 5 to 10 timesless than in conventional inflators. Also the surface area for heatdissipation is significantly larger in an elongated aspirated inflator.Finally, since somewhat toxic propellants can now be used which leavevery little residue and since cooling screens in many cases are notrequired, the amount of heat that remains in a gas generator for anaspirated inflator, and now also for many other inflator designs, isconsiderably less in comparison to the heat transfer area and thusplastic becomes a viable material for inflator construction. A preferredplastic is a glass or mineral-filled polycarbonate.

As mentioned elsewhere, the use of aspirated inflators on the sidecurtain, for example, provides several occupant protection advantages.If the occupant is in the path of the deploying airbag and interactswith it, the pressure within the airbag will increase which will alsoreduce the aspiration ratio and thus automatically adjust to theoccupant without injuring him or her. Secondly, since gas from thepassenger compartment is used to inflate the airbags, the total pressureincrease within the vehicle is substantially reduced allowing manyairbags to be deployed at the same time. In many accidents, for example,it is desirable to deploy both frontal driver and passenger airbags aswell as side curtain airbags. In fact, there is some advantage in doingthis routinely for all accidents that require either a side or frontalairbag.

Referring now to FIG. 531, the housing 440 of the inflator module 439 iselongate and FIG. 531 shows a cross-sectional view in the longitudinaldirection through the approximate center of the housing 440. Thus,opening 441 is shown and is elongate as is housing 440. Further, it canbe seen that the igniter mix 445 is arranged over the propellant 444 toseal the propellant 444 from the atmosphere, as noted above, and thus,the igniter mix 445 is present along the entire length of the propellant444. In other words, the igniter mix 445 is substantially coextensivewith the propellant 444. One advantage provided by the presence ofigniter mix 445 over the propellant 444 is that the propellant 444 willburn at all locations along its length at the same time. Gas will thisbe released over the entire length of the inflator module 439 and thusover the entire length of the airbag 433. This will enable the airbag433 to be inflated evenly across its length.

In contrast to the use of igniter mix coextensive with propellant, someinflators have the igniter positioned at the ends of the propellant sothat the propellant burns from its ends. Examples of such constructionsinclude Grace et al. (U.S. Pat. No. 6,062,143), Hamilton (U.S. Pat. No.4,696,705) and Goetz et al. (U.S. Pat. No. 4,698,107). Using suchinflators to inflate an airbag, gas would be released in directions fromthe ends toward the center and inflation of the airbag could be uneven,depending for example, on the manner in which the gas is subsequentlydirected and the shape of the airbag.

As should now be evident, the aspirated inflator of the presentinvention has significant advantages over other aspirated inflatorscurrently used in conventional airbag systems. In particular, largeopenings are provided in the form of the inlet ports 450 on either sideof the aspirating nozzles. These ports 450 permit the flow of gas fromthe passenger compartment 459 into the aspirating nozzle through ports450 with a short, low flow resistance, flow path. Once the cover 452 isremoved from the airbag system and initial airbag deployment has begun,the module pops open and the inlet ports 450 are open to allow theentrance of the passenger compartment gas. The outlet passage from theinflator passes through a converging-diverging nozzle as described abovewhich causes a smooth developed supersonic flow pattern in the emerginggas. The gas leaves the nozzle 436, 437, 438 at exit 449 and enters themixing chamber 447 at a position near the throat of the aspiratingnozzle 435 defined by walls 456 and shields 455 after which theaspirating nozzle 435 diverges, see FIGS. 53C and 53D, to create theminimum pressure at the throat to aid in drawing in the maximum amountof gas from the passenger compartment 459 through inlet ports 450. Usingthis design, total pumping ratios of up to 10:1 of passengercompartment-to-generated gas result and instantaneous ratios of up to20:1 have been proven feasible.

The deployment of the airbag 433 is timed so that, as shown in FIG. 53D,after the airbag 433 is fully inflated and the gas generator 439 hasstopped generating gas, i.e., all of the propellant 444 has been burned,the occupant begins to press against the deployed and inflated airbag433. As a result of the impact of the occupant against the inflatedairbag 433, the gas in the airbag 433 begins to flow back through thenozzle 435 defined by spring shields 455 and walls 456 and back out intothe passenger compartment 459 through the aspiration inlet ports 450,which thus function as outlet ports at this juncture. Accordingly, thepressure or amount of gas in the airbag 433 is controlled based on theoccupant or the occupant's position, i.e., based on the interaction ofthe occupant with the airbag 433, gas begins to flow out of the airbag433. In view of absence of gas flow from the gas generator 120, thenozzle 435 defined by spring shields 455 and walls 456 is smaller thanduring the flow of gas from the gas generator 439 and, the supportsprings 451 pull walls 456 closer to the base 434 thereby reducing thesize of aspiration inlet ports 450. By this method and design, the flowresistance of the aspiration inlet ports 450 for this return flow will,by design of the support springs 451, be optimum regardless of theparticular propellant used or the particular airbag geometry. Othergeometries and structures are possible which, for example, entirelyclose off the exhaust ports after the gas generation has stopped andonly open when the pressure within the airbag increases above a designedvalue.

Thus, after the propellant 444 in the tube 440 has finished burning, asa result of a pressure difference between the area proximate and withinthe gas generator 439 and the interior of the airbag 433, the gas insidethe airbag 433 will be caused to flow back through the aspiration inletports 450, in a direction opposite to that during inflation of theairbag 433, gradually exhausting the gas from the airbag 433. This onlyhappens, however, when the pressure in the gas generator 439 drops,which is indicative of the end of the burning process. In this manner,the gases produced by the gas generator 439 are always cooled by theaspirated air through inlet ports 450 and there is no need for coolingscreens inside the gas generator 439.

If an occupant interacts with the airbag 433 during its initialinflation phase before the cover 452 is expelled in one preferreddesign, the pressure in the chamber 447 will rise, the flow of gas intothe airbag 433 in preparation for deployment will be stopped, and gasfrom the gas generator 439 will flow out through aspiration inlet ports450. This also constitutes control of the pressure or amount of gas inthe airbag 433 based on the occupant or the occupant's position, i.e.,based on the interaction of the occupant with the airbag 433, thepressure and amount of gas in the airbag will be changed and probablyreduced. This construction prevents injury to an occupant who is loadingthe cover 452, i.e., resting against the same, prior to inflation of theairbag 433 in the manner described above. In current airbag moduledesigns, if an occupant loads the airbag cover or casing, the pressurewill continue to build up behind the cover until thousands of pounds offorce are available to force the cover open and thereby injure or killthe “out-of-position” occupant. In another preferred design, theaspiration inlet ports are not uncovered until after the cover isreleased and the airbag is partially deployed. Since the total motion ofthe module surface is still small compared with conventional airbagmodules, the injury sustained by the occupant is minimized.

An additional advantage to using the aspirating ports 450 as the exhaustports for an “out-of-position” occupant is that gas does not startflowing out of the airbag 433 until the gas generator 439 stopsproducing gas. In contrast, in current airbag module designs, the gasbegins flowing out of the airbag immediately as the airbag is beinginflated. The design that is described herein, therefore, conservesinflator gas and permits the use of a smaller amount of propellant inthe inflator. The combination of this effect and pressure compensationeffect described above can reduce the amount of propellant required toinflate the airbag by a factor of two or more, thus again substantiallyreducing the size and cost of the inflator and the quantity of toxicgases which are exhausted into the passenger compartment and wideningthe class of propellants available for use with airbags. The totalcompartment pressure rise which results from the deployment of multipleairbags is also substantially reduced. However, even if a significantamount of toxic gas is exhausted into the passenger compartment duringdeployment of the airbag, the sensor and diagnostic module 458 may becoupled to a number of different arrangements for reducing theconcentration of toxic gas in the passenger compartment resulting fromthe deployment of multiple airbags or unconventionally large airbags(which aspect is discussed in greater detail below). Thus, the airbagmodule 430 described above may be implemented in a comprehensive airbagsystem in connection with a toxic gas reducing arrangement.

As discussed above, in some situations with conventional inflators, butnot with the inflator of this invention, the occupant may be soout-of-position as to be already leaning against the airbag module whenthe sensor and diagnostic module signals that the airbag should bedeployed. This is a particularly serious situation since deceleration ofthe vehicle may cause the occupant to exert a significant force againstthe airbag cover preventing it from opening. The inflator module willbegin producing gas and if the flow out of the inflator module isresisted, the pressure in the inflator module will increase, evenexceeding about 1000 psi if necessary, until the resistance is overcomeand the cover opens. This can result in very large forces against thehead or chest of the occupant and result in serious injury or evendeath.

Several inflator designers and manufacturers are experimenting withvariable output inflators where the gas flow from the inflator isreduced. However, this will not solve this problem but only delay thepressure buildup for a few milliseconds with the same eventualcatastrophic results. The design used herein eliminates this problemsince even though the occupant may load one portion of the cover 452 atone location in the longitudinal direction of the cover 452 preventingit from opening by the release of latch 453, and even if he were able toentirely block the removal of the cover 452, the build-up of gas in themodule 430 will cause a slight bulge in the cover 452 causing it to popfree of the base 434 and the gas will begin flowing out through inletports 450 as soon as the pressure exceeds a design value which issignificantly below that required to oppose the force of an occupantleaning against the airbag module cover 452. However, for many of thepreferred mounting locations of the airbag module 430 of this invention,such as on the ceiling of the vehicle, it is very difficult for theoccupant to get into a position where he/she is against the module cover452. Also, note that for some applications, some additional motion ofthe cover 452 is permitted in order to permit an initial airbagdeployment before aspiration begins.

In conventional airbag module designs, the cover is cut open during thedeployment process. The expulsion method used here has the advantage ofsimplicity since no cutting of material is necessary and it also permitsa rapid opening of the aspiration inlet ports which is important to theinflator design disclosed herein. If properly designed, the coverrelease mechanism requires little force to release the cover and yet isvery difficult to detach from outside the module. Thus, the cover isreleased before significant pressures occur in the module, reducing thedanger of deployment-induced injuries to the occupants.

Another preferred embodiment of the invention in which there issufficient space for the formation of aspirating channels behind themounting surface on which the airbag module is mounted is illustrated inFIGS. 54A and 54B. Aside from the direction of movement of the airbagmodule 430 to open aspirating channels, the operation of this embodimentis essentially the same as the embodiment discussed above. However, incontrast to the embodiment in FIGS. 53A-53H, in this case, the gasgenerator 439 and base 434 are displaceable and are moved away from amounting surface 463 in one direction during airbag deployment whereasthe airbag 433 is deployed in an opposite direction. To enable thisrelative movement of the gas generator 439 and base 434 relative to thefixed mounting surface 463, the leg portion 456 a 2 of each of the walls456 is attached to the mounting surface 463. As shown in FIG. 54A, thebase 434 is mounted in engagement with the mounting surface 463 on oneside thereof, which is the side to which the walls 456 extend. On theopposite side of the mounting surface 463, the latches 453 are mountedso that the cover 452 is detachably connected to the mounting surface463 by tabs 454 engaging with the latches 453. Thus, in this embodiment,instead of connecting the base 434 to, e.g., the ceiling of the vehicleas in FIG. 52, the walls 456 are connected to the mounting location,such as the instrument panel or knee bolster structure, of the vehicleand would not be substantially displaced during deployment of the airbag433. In this context, the instrument panel of the vehicle is defined soas to include the knee bolster area of the vehicle from which airbagsused as knee bolsters would be deployed.

In an alternative embodiment, the inflator module 433 can be mounted ina position with the aspirating ports 450 open provided there issufficient space available and thus, this invention is not limited tothe preferred embodiments whereby the inflator module 433 expands ondeployment.

One particular application for the design of FIG. 54A is for use as aknee protection airbag as shown in FIG. 55. FIG. 55 illustrates apreferred embodiment of the present invention used as a knee protectiondevice for the driver and front passenger occupants. The airbag moduleis shown deployed generally at 465 in FIG. 55 and includes an airbag466. The airbag 466 is designed to interact with the driver's knees, notshown, and with the body of an occupant who may be lying down, also notshown. In this manner, the airbag 466 protects not only the knees of thedriver from injury but also protects a child lying on the front seat,for example.

Knee airbags have previously been commercially used only as part of thefront passenger airbag system where they have been inside of and inconjunction with the passenger airbag and inflated by the passengerairbag inflator. Current front passenger airbag systems are all mid orhigh-mount systems where it is no longer convenient to mount a kneeairbag inside of the passenger airbag or to use the same inflator. Theexemplifying embodiment shown in FIG. 55 uses a separate airbag systemwith its own inflator. This is made practical by the low cost efficientairbag module design disclosed herein. The airbag module 465 forcontrolling inflation of the knee airbag 466 may have any of theconstructions disclosed herein.

FIG. 56 illustrates another possible mounting location for the airbagmodule, shown generally at 467, in accordance with the invention andincluding a deployable airbag 468. In this embodiment, the airbag 468,also called a curtain airbag, will be deployed from the ceiling in theevent of a side impact of sufficient severity that an occupant's headwould otherwise be injured. This implementation is significant since theairbag for the front and rear seats are combined, i.e., the airbagdeploys along substantially the entire side of the vehicle alongsideboth the front seat and the rear seat, which results in significantlygreater protection in side impacts when the windows are broken. Theairbags are less likely to project outside of the windows if they arerestrained by the B-pillar 469 and other vehicle structures such as theA-pillar 461 as shown in FIG. 52. This support is achieved since themodule extends forward almost to the windshield and is mounted adjacentto but somewhat away from the side of the vehicle. When the airbagdeploys, therefore, it is partially restrained by the A-pillar furtheraiding the retention of the occupant's head within the vehicle. As notedabove, airbag 468 may comprise a number of airbags controlled to deploysimultaneously by means of a common inflator system and the airbagmodule 467 for controlling inflation of the side airbag 468 may have anyof the constructions disclosed herein.

2.1.2 Steer by Wire

The steering wheel and steering column are among the most dangerousobjects in the automobile. Even with airbags and seatbelts many peopleare still injured and killed by an impact with a steering wheel rim,spokes or hub, or by the airbag as it is deployed from the steeringwheel hub. The steering column also significantly interferes with theoperation of many knee bolster designs causing significant leg and kneeinjuries. With today's technology, neither the steering wheel norsteering column are necessary and only bring harm to drivers. Asubstantial educational program is necessary to wean people away fromthe false feeling of security of a substantial steering wheel andsteering column. However, if it can be shown to the population that avehicle with a servo electronic steering system (called steer-by-wire)is considerably safer, then the battle can be won. Such a system iscommon in commercial aircraft although a steering wheel is still usuallyused.

One implementation of a driver protection airbag system which isdeployed from the ceiling 476 coupled with a steer-by-wire system isillustrated at 470 in FIG. 57 which is a partial cutaway view of adriver in an automobile. The conventional steering wheel and column havebeen eliminated from this vehicle and a thinner, lighter steering wheel472, which projects from an instrument panel 473, is provided instead.The steering wheel 472 is attached to a deformable column 474 which issupported by the instrument panel 473. In the event of an accident, thesteering column 474 easily bends at the connection point 475 with theinstrument panel 473 and permits the steering wheel 472 to be displacedor to be rotated out of the way, i.e., to make room for the deployingairbag as illustrated in FIG. 58. In this embodiment, a single airbag471 is deployed downward from the ceiling 476 to protect all occupantsin the front seat of the vehicle, and thus is elongate extendingsubstantially across the entire width of the passenger compartment ofthe vehicle.

If some energy absorption is desired, the steering wheel support 474 canbe made in the form of an elastica spring which has the property that itwill provide a nearly constant force versus deflection relationshipwhich can be designed to aid the energy absorption of the airbag. Thesteering wheel and support in FIG. 57 is shown with the airbag wrappedaround which somewhat reduces the energy absorption effects of theairbag. Other implementations are to pull the steering wheel into theinstrument panel space using pyrotechnics, a mechanical linkage (as inthe Pro-Con-Tem system) or to release the support so that the airbagitself moves the steering wheel out of the way. If alternate steeringsystems can be sold to the public, the steering wheel and support can beeliminated entirely and replaced by a device mounted onto or between theseats or on the floor, for example. Even steering mechanisms mounted tothe door or ceiling are possible. Many other steering systems which donot interfere with the airbag will now be evident to those skilled inthe art. One might be to have the steering wheel collapse at a constantacceleration.

FIG. 58 illustrates the positions of front and rear seat airbags as wellas of the steering wheel and steering support after the airbags havedeployed and the occupants have begun moving forward. Deployment of thefront and rear seat airbags may be controlled to occur simultaneously.

2.1.3 Rear of Seat Mounted

FIG. 59 illustrates another implementation of the airbag module of thisinvention in which the module 477 is mounted to the rear of the frontseats 478 of the vehicle and is designed for those cases where aceiling-mounted system is not desired or practical. In this case, twoairbag modules 477 are provided, one in the back of each of the frontseats 478. A single airbag can be used for vehicles with bench seats.

A primary advantage of the linear, elongated module disclosed herein isthat it can be mounted on the surface of the ceiling, instrument panel,seat back, or other appropriate surface. In some cases, the module isliterally attached to the mounting surface while more commonly it isrecessed so that the surface of the module is approximately flush withthe surrounding surfaces prior to deployment. In most cases, however,the depth of penetration into the mounting surface will be small andless than 115 of the module length and in most cases less than 1/10 ofthe module length. For the purposes of this disclosure, therefore,mounting on a surface will mean mounting so that the penetration intothe surface will be less than ⅕ of the module length.

2.2 Aspirated Inflator

2.2.1 Plastic Inflator

A preferred material for the gas generator housing of this invention issteel in order to withstand the pressure and temperature from theburning propellant. It is possible to make the inflator housing from ahigh temperature plastic, however, the propellant tube in this case willbe considerably thicker. Plastic can be used in the inflator of thisinvention since the propellants generally used burn completely in a veryshort time period and do not leave a hot residue. Thus, there is littletime for the heat to penetrate into the plastic housing. For this samereason, the inflator of this invention can be mounted adjacent tocombustible materials without fear of starting a fire.

In the preferred embodiment of the airbag module of this inventionillustrated in FIGS. 52 and 53A, the length of the module wasapproximately the same as the length of the airbag. This permits theairbag, especially if made of film, to be easily rolled or folded withthe portions of the airbag which project beyond the module easilyaccommodated without the special endwise folding required inconventional inflators. This results in a uniform geometry and symmetryfor the airbag module and permits the module to be easily made in anyconvenient length. Additionally, the long, thin design permits themodule to be bent somewhat so as to conform to the surface of thelocation where it is mounted. This geometry also permits the airbag tounfold much more easily and in considerably less time than withconventional designs. Thus, the airbag system of this invention can bedeployed in less time with less force and thus with less danger ofdeployment induced injuries than with conventional designs.

In a particular example used in this application, the cover ismechanically pushed off by the expansion of the airbag, or thedisplacement of the module, progressively from one end to the other muchlike a zipper. In other applications it may be required topyrotechnically cut or eject the cover which would require separatepyrotechnic devices. Also, in the examples illustrated herein, themodule cover has been pushed off and removed from the module. Althoughthis is the preferred method, other designs could remove the cover bycutting an opening in the material which covers the module. In suchcases, the existence of the module could be completely hidden throughthe use of a seamless covering and only cut open when it is required fordeployment of the airbag. For the purposes herein, therefore, removal ofthe cover will include any method by which an opening is provided topermit the airbag to deploy.

2.2.2 Variable Burn Rate

The propellant and gas generator assembly has been shown with anapproximate rectangular cross section so that once the propellant beginsburning the surface area neither decreases or increases as the inflatorpropellant is consumed. In some cases, it may be desirable to vary theburn rate of the propellant by changing the surface area which isburning. If the cross section area of the inflator, and thus of thepropellant, were made triangular, for example, with a wider base andnarrower top, the rate of gas generation would increase as thepropellant burns. Conversely, if the base of the propellant werenarrower than the top, the opposite would occur and the propellant willbegin burning fast and slow down with time. The shape of the inflatorhousing can be infinitely varied to achieve any reasonable variation inpropellant burn rate with time desired. For complicated shapes, it isnecessary to cast the propellant in place in the tube which also helpsthe propellant to adhere to the surfaces of the gas generator housing.

2.2.3 Liquid Propellant

U.S. Pat. No. 5,060,973 discloses the use of a liquid propellant.Central to this patent is the method of injecting the liquid from itscontainer into a combustion chamber. A liquid propellant has animportant advantage that many such propellants, and the particular onedisclosed in this patent, burn without producing solid particles whichcould clog the high pressure nozzle or burn holes in a film airbag. Thepurpose of the injection system is to control the burning rate of thefuel. In solid fuel inflators, this is done by shaping the surface ofthe propellant as discussed above.

The burning surface can also be controlled in the geometry of theinflator in accordance with the present invention by increasing theviscosity of the liquid through an emulsifying process or, alternately,by placing a solid matrix within the tube which is non-combustible suchas one made from glass fibers. These fibers therefore serve to hold theliquid propellant in a position where the burning surface area is knownand thus the burning rate controlled. Other methods of controlling theliquid burn rate without resorting to an injection system will nowbecome apparent to those skilled in the art.

In addition, the liquid propellant can be used in a separate inflatorhousing such as discussed with reference to FIG. 53H. This invention isnot limited to the use of liquid or solid propellants but alsocontemplates the use of stored gas, hot gas, hybrid or other designs.

2.2.4 Propellant Considerations

As mentioned above, several propellants, including nitrocellulose,nitroguanidine, and other double base and triple base formulations andtetrazol, now become candidates for use in vehicles with more than oneairbag module. One of the primary advantages of this invention is thatthe gases produced can be breathed for a short time by occupants withoutcausing injury. The time period would of course depend on the vehicleand the method chosen for exhausting the toxic gas from the passengercompartment. All such propellants that fall into this class, that ispropellants that can be safely breathed only for short periods of time,are referred to here as toxic airbag propellants. Other propellants ofcourse exist which are so toxic that they would never be considered ascandidates for airbag inflators. This class of propellants is not evenconsidered here and therefore falls outside the class of toxic airbagpropellants as used herein. Toxic, as applied to a gas for the purposesherein, generally means non-breathable for more than a few minuteswithout causing harm to humans.

2.2.5 Cover Considerations

A perspective view of a preferred cover design is shown generally as 452in FIG. 60. It comprises a semi-rigid molded plastic backing material480 covered with a foam 481 and skin 482 or other combinations ofmaterials to be compatible with the vehicle roof liner, instrument panelor other mounting location. Tabs 454 are placed in the cover tointerlock with corresponding catches 453 on the module housing base.When pressure builds beneath the airbag, it causes the airbag to bulgepulling tabs 454 out of engagement with catches 453 in the progressivemanner as described above. The cover 452 is then free to move and willin general be projected downward by the deploying airbag. It has a lowdensity, however, and will not cause injury even if it impacts anoccupant.

In the example shown in FIG. 60, the cover 452 can be attached to theairbag by an adhesive or other suitable means. When the airbag deploys,the cover 452 adheres to the airbag on the side away from the occupantthereby generally preventing interaction between the occupant and thecover 452.

With the development of the film airbag as described in the patentsreferenced above, and the inflator design described herein, a very thinairbag module is possible which can be made in any length. Typically,the module length will exceed about 10 to 20 times the width orthickness of the module, and in all cases at least about 5 times. Thelength of the gas generator will typically be about 40 to 80 times itsthickness and in all cases at least about 10 times. This shape permitsthe module to be easily mounted in many locations and to be bent orcurved to match the interior shape of the vehicle. For example, onecould be positioned so as to conform to the ceiling to protect rear seatoccupants. Another one could stretch the length of the car on each sideto protect both front and rear occupants from head injuries in sideimpacts. A similar system can be used for a deployable knee bolster, andeventually a single module can be used for both the passenger and driverin frontal impacts when used in conjunction with a servo electronicsteer-by-wire system, for example. With the economies described above,airbags of this type are inexpensive compared to current airbag systemsoffering comparable, or inferior, protection.

The airbags described herein would be easily and inexpensivelyreplaceable. They would require only a single connection to the vehiclesafety system. Although the bags themselves would not be reusable, insome cases the airbag covers could be.

The designs illustrated herein are simple and, because of their smallcross-section, can be easily mounted to conform to interior vehiclesurfaces. They are very efficient, in some cases requiring less than ⅕of the amount of propellant that is required by competitive conventionalsystems. The particular designs are also easily manufactured. Since theyuse less propellant, the noise and problems with high pressures whenmultiple airbags are deployed are greatly reduced. They also offerprotection in cases such as the sleeping child which has previously notbeen available. These designs as disclosed herein, therefore, provideall of the objects and advantages sought.

Furthermore, several different airbags are shown for protectingoccupants of the vehicle, i.e., the rear airbag 430 shown in FIG. 52,the knee airbag 466 shown in FIG. 55, the side airbag 468 shown in FIG.56 and the front seat airbag 471 shown in FIG. 57. Simultaneousdeployment of any combination of or even all of these airbags may beinitiated by the sensor and diagnostic module 458 upon determining thata crash requiring deployment of such airbag(s) is required. Thus, thesensor and diagnostic module 458 may determine that deployment of onlythe front airbag 471, knee airbag 466 and the side airbag 468 aredesired, for example in the case of a frontal crash, or possibly onlythe side and rear seat airbags 468, 430 in the event of a side impact.Accordingly, sensor and diagnostic module 458 may be designed to detectfrontal impacts requiring deployment of airbags as well as side impactsrequiring deployment of airbags and rear impacts requiring deployment ofairbags.

In the following, a vehicle having multiple airbags, preferably arrangedin connection with any one of the constructions of the airbag moduledescribed above (but which arrangement is not essential to theinvention), is described in conjunction with toxic gas reducingarrangements which serve to reduce the concentration of toxic gas in thepassenger compartment during or after deployment of the airbags. Thesetoxic gas reducing arrangements may of course also be used even forvehicle with only a single airbag.

A perspective view of a vehicle having several deployed airbags for bothfront and side protection is shown in FIG. 61. The vehicle includesfrontal protection airbags 485, 486, 487, 488 and side/head protectionairbags 489, 490, each of which is coupled to an airbag module (notshown) whereby each module may include one or more airbags as well as agas generator for inflating the airbag(s), the airbag(s) being attachedto and in fluid communication with the gas generator, and an initiatorfor initiating the gas generator in response to a crash of the vehicle.A rear window 493 of the vehicle has been broken or ejected for thereasons and in the manner described below. The driver side frontalairbag 485 has been deployed as well as the ceiling-mounted side headprotection airbag 489. In this case, the sensing system for controllingthe deployment of the airbags, not shown but which is coupled to all ofthe airbag modules, detected that the crash had an angular componentwhich might have resulted in head injuries to the occupant from impactswith an A-pillar 491 or a side window 492 of the vehicle, so the sensingsystem determined that deployment of the side head protection airbags489 and 490 was warranted, along with deployment of the frontalprotection airbags 485, 487 and 488. The front passenger seat wasunoccupied, which was detected by the occupant position sensor, notshown, and therefore the corresponding frontal protection airbag 486 andleft side protection airbags (not shown) were not deployed. Since bothrear seats were occupied, the appropriate rear seat protection airbags487, 488 and 490 were deployed. It is thus possible to selectivelycontrol or determine which airbags of a plurality of airbags, e.g.,side/head protection airbags, frontal protection airbags, in a passengercompartment of a vehicle should be deployed depending on the crashconditions to thereby avoid unnecessary airbag deployment. Although thesensing system which determines which airbags require deployment is notshown, this system may include or be connected to occupant sensing meansfor sensing which seats are occupied.

2.2.6 Driver Side Aspirated Inflator Airbag Module

Aspirated driver side steering wheel mounted aspirated inflators andairbag modules are illustrated in FIGS. 126A and 126B, for a nonrotating inflator, and FIGS. 127A and 127B for a more conventionaldesign where the inflator rotates with the airbag module. Both cases cansolve the “punch out” problem wherein when a person in leaning againstthe airbag the pressure builds in a conventional driver airbag untilsufficient force is available to push the driver away from the airbagallowing the cover to open. In the designs of FIGS. 126A-127B, themaximum force that is applied to open the cover is controlled and whenthe cover meets a resistance, such as provided by an out-of-positionoccupant, the airbag does not deploy and the propellant gasses areexhausted through the aspiration valve eliminating the need forcomplicated control systems such as disclosed in U.S. Pat. No.6,206,408.

In FIG. 126A, a sectioned view of the airbag module is shown generallyat 914. An aspirated inflator assembly 915 contains a small pyrotechnicgas generator 917 which provides the high pressure gas flow to induceair from the passenger compartment to flow through the valve 916 andnozzle 918 into the airbag 919.

In FIG. 126B, the propellant 921 is distributed symmetrically around theouter wall of the inflator. Naturally, it could also be placed elsewheresuch as the inner wall. The principle of operation is essentially thesame. Felt pads or bearings 920 are also used.

In FIGS. 128 and 129, two versions are illustrated for the case wherethe inflator is attached to and rotates with the steering wheel.

2.2.7 Enhanced Aspirated Inflator

Appendix 3 contains a brief discussion of the use of vortex flow controlmethods to further improve the performance of an aspirated inflator.This will provide the basis of future patent applications.

2.3 Controlling Amount of Gas in the Airbag

2.3.1 Production of Gas

Let us consider again FIGS. 53A-53G. In general, the burn rate ofpropellants increases with ambient temperature and also with pressure,the so-called pressure exponent. This is expressed in the followingequation:W=kP ^(n)

where: W=the mass flow rate, k=a constant that depends on the propellantproperties and burn surface area and n=pressure exponent.

The pressure exponent can be determined by the slope of a line drawn ona log-log plot of burn rate versus pressure from experiments for theparticular propellant species and formulation. The pressure exponent forpropellants such as sodium azide is approximately 0.4 or less. Recentlypropellants have been developed having a higher pressure exponent above0.4.

The flow out of a restrictor in the inflator generally follows theorifice equation for supersonic gas flowW=Ak(P/r)^(0.5)

where: W=the mass flow rate, P=The pressure in the inflator, A=The crosssection area of the restrictor, K=the orifice coefficient for thedevice, and r=The density of the gas in the inflator.

The techniques described here (first reported in U.S. Pat. No.5,772,238) are used to control the pressure in chamber 442 to offset theoften uncontrollable changes in ambient temperature. By keeping thepressure in chamber 442 relatively constant through the techniquesdescribed above, or even decreasing the pressure in chamber 442 withtemperature, the propellant burn rate is kept approximately constant.This serves to reduce the variation in the inflator gas output as afunction of temperature. At cold temperatures, when the propellant tendsto burn slowly, the clearance at throat 437 will be reduced and thepressure will build up increasing the propellant burn rate (as governedby the burn rate equation above) until the flow of gas out of chamber442 (which is governed by the orifice equation above) is sufficient torelieve the pressure. Similarly, at high temperatures, when thepropellant tends to burn at a higher rate, the pressure will be relievedreducing the pressure and slowing down the burn rate. In this manner,the invention provides a self-correcting system for providing asubstantially constant propellant burn rate, based on adjustment inpressure in the chamber 442, regardless of the ambient temperature. Thisprinciple can also be used to vary the inflator burn rate as a functionof time, the severity of the crash and/or the vehicle occupancy.

Conventional inflators, which do not have this pressure adjustingmechanism, produce higher gas flow rates at high ambient temperaturethan at low temperature since the resistance to the gas flow rate out ofthe inflator ports is constant. Therefore, a greater gas generatingcapacity is required at cold temperatures than at high temperatures andthe inflators must be designed with sufficient propellant to handle thecold temperature case. Thus, a larger quantity of propellant is neededfor conventional inflators by as much as a factor of two than would bethe case in the inflator described above.

A further advantage of the elastic pressure adjustment system describedabove is that since the inflator nozzle 436, 437, 438 opens as afunction of the pressure in the chamber 442, it would not be possiblefor the inflator module 439 to explode in a fire which can be a problemin conventional designs. Thus, in general, a device called a “match” orauto-igniter which is used in conventional inflators to start thepropellant burning in the case where the vehicle is on fire, forexample, is not required for the gas generator described hereinparticularly when the elastic brackets 457 are used. It is also ingeneral not required since the total amount of propellant used is smalland it is distributed along a significant length. Thus, the confinementpressures required for the propellant to detonate do not occur in thisdesign rendering this design inherently safer than the design ofconventional inflators.

The principles of flow control out of an inflator to achieve a desiredpropellant burn rate can be applied to all inflator designs for use intemperature compensation as well as the general flow control for thedesired inflation amount and rate of an airbag. It is not limited toaspirated inflators nor to the particular airbag module designsdescribed herein. The flow restrictor can have any shape and is notlimited to the geometries of the embodiments disclosed herein. Thevariation in flow rate can be a constant, or any other time varyingfunction as selected by the controller described below. This control isaccomplished in general without the need to monitor the inflator gasproduction or flow properties directly as disclosed in U.S. Pat. No.6,314,889, for example, and in the variable case, the controller caneffect the area of the exhaust orifice(s) in any of a variety of methodssuch as through an electrical actuator. Such an actuator can control avalve opening, the pivot point of a spring-loaded obstruction that atleast partially obstructs the flow out of an inflator, the forceopposing the opening of an exit port of an inflator and/or the area ofthe exit port directly, for example, according to the desires of theinflator designer. Even an array of MEMS micro valves can be an optionallowing simple and direct control by the controller or actuator. Oncethe principle of varying the gas production rate as taught herein and inassignee's pioneering patents is known, the use of this principlebecomes obvious to those skilled in the art as evidenced by U.S. Pat.No. 6,314,889.

Different propellants have different rates of combustion which has asignificant effect on the geometry of the gas generator. For propellantswith slow burn rates, the ratio of the burning surface width to thethickness of the solid propellant will have to increase. For slowburning propellants, therefore, the width of the tube 440 in a directionparallel to the igniter mix 445 may be much larger than the thickness ofpropellant 444. In other cases, the width of the tube 440 might becomesignificantly less than the thickness of the propellant 444. This designtherefore can accommodate a wide variety of propellant chemistries, andparticularly those which produce small amounts of toxic gas which havepreviously been unusable, and therefore design is not limited to anyparticular propellant.

In particular, FIG. 53G illustrates a case where a very slow burningpropellant 444 is used and thus a wide thin geometry has been chosen forthe inflator module 439. In this case, a tube is not used and theinflator module comprises the propellant 444 which is attached by anadhesive to a piece of formed metal 462 or other similar memberpositioned to define a constricting nozzle with the base. This geometryhas the significant advantage of simplicity as can be readily seen inthe illustration. It has another advantage in that propellants havingslow burn rates can be used which previously could not be used. Slowburn rate propellants require very thin structures with a large surfacearea. If such propellants are formed into tablets as is conventionallydone in conventional inflators, they would lack sufficient structuralstrength and be prone to breakage. If the tablets break, the surfacearea is increased and the propellant burns faster. This would be anuncontrollable property of these tablets such that the burn rate ofvarious inflators depends on how many tablets break. Since this isunacceptable, there is a practical lower limit for the burn rates forpropellants used in conventional inflator designs. This, therefore,restricts those classes of propellants which can be used. Thisrestriction does not apply to the present invention since the propellant444 is supported by metal piece 462 and therefore can be made very thinwithout fear of breaking. The metal piece 462 is also provided withappropriate curved sections to define a converging-diverging nozzle 436,437, 438 with the support base 434. Also in this embodiment, a layer ofigniter mix 445 may be coated onto the propellant 444.

2.3.2 Control Module

Smart airbags are covered in detail below and this disclosure, whichoriginally appeared in U.S. Pat. No. 0,577,2238, will not be repeatedhere. However, some elaboration is desirable on the control moduledisclosed therein. Although since that patent did not cover particularmethods of controlling the flow into the airbag as discussed above, anymethod for controlling such an inflow is contemplated herein and in the'238 patent. In particular, the control of the rate of gas production byan inflator as well as the control of the percentage of gas that goesinto a particular airbag (an inflator can inflate more than one airbag),or the aspiration ratio for aspirated airbags by any method iscontemplated herein. Also, as discussed below and elsewhere herein, theparameters that are used to effectuate such control through the controlmodule include, among others, the output of any crash sensors (includinganticipatory crash sensors), any occupant sensors that determine what ispresent in the vehicle, its size and/or weight, and where it is located.All possible technologies that can be used are contemplated including,for example, ultrasonic, optical, electromagnetic wave or electric fieldspatial sensors, bladder, strain gage or any other weight sensor, or anysensors that physically monitor the motion of the occupant such asseatbelt load or acceleration sensors or accelerometers or other sensorsthat physically monitor the acceleration, velocity or position or anoccupant such as accelerometers that directly measure the accelerationor position of an occupant or the pressure in an airbag that interactsan occupant or the tension in a seatbelt being used by an occupant. Thecontrol module generally contains a microprocessor which receives inputsfrom one or more of the above listed sensors and through an appropriatealgorithm, which can be based on or use a neural network, determines thedesired gas flow into or out of a particular airbag or group of airbags.The particular method of effectuating this control depends on which ofthe many structures and methods is/are chosen by the system designer andto delineate in detail all such combinations would require volumes. Theparticular designs are therefore left to those that are skilled in theart of each of the particular structures or methods chosen. Generally,sensors that directly measure the gas pressure, flow or temperature asit leaves the inflator as is disclosed in U.S. Pat. No. 6,314,889 wouldgenerally not be used based on the difficulty of making suchmeasurements reliably. Rather, the result of the flow into the airbag isthe preferred approach. This result can be measured by monitoring themotion of the occupant through any of the occupant sensors listed aboveand/or by monitoring the pressure and/or volume of the airbag itself. Apreferred approach is to monitor the acceleration imparted to theoccupant by the airbag.

One method of controlling the amount of gas in an airbag is to controlthe aspiration ratio. Aspiration ratios of as high as 7 have beenexperimentally achieved by the assignee's scientists. The aspiration ofgas from the passenger compartment into an airbag allows the temperatureand the quantity of the gas in the inflator to be controlled. Theaspiration ratio of a particular inflator can also be controlled bycontrolling the position of the valves that allow the gas to flow intothe aspirator from the passenger compartment and which close at the endof the inflation process, by diverting some of the inflator hightemperature and pressure gas from going through the aspirator, or bymany other methods that will not become obvious to those skilled in theart.

The controller described herein can operate in any of several modes. Itcan receive information continuously from various sensors andcontinuously adjust the flow into or out of one or more airbags, forexample. Alternately, it can process the various sensors and set aschedule for the flow into and/or out of the airbag at the beginning ofthe process and then not modify it afterward. The latter approach ofcourse would be less accurate but result in a less expensive processorand control module circuitry. In either case, intelligence can beincluded in the algorithm covering, for example, the relationshipbetween the orifice area and the gas flow rate out of the inflator thussimplifying the control process. In one example, a model of the entiresystem can reside in the processor and the effect of any sensor inputcan then be determined and the flow adjusted appropriately. Alternatelyor additionally, a neural network can be used and the correlationbetween the desired gas flows and the sensor inputs determinedexperimentally. Of course, any combination of the above methods also canbe used.

2.3.3 Control of Gas Outflow

Control of the outflow of gas from one or more airbags can beaccomplished by varying the opening of an exhaust port in the airbag orthe inflator as desired. Controllable valves or vents within an airbagare discussed in section 3.8 below. The outflow can also be controlledas part of an aspirated inflator through control of the opening of theaspirating ports, for example.

2.4 Exhausting Inflator Gas

2.4.1 Removing Window

As described above and in U.S. Pat. No. 5,505,485, a desirable inflatorfor use in this airbag system is of the non-sodium azide highlyaspirated type and the most desirable airbags are made from plasticfilms. It is contemplated that the inflators of the '485 patent may beused in accordance with the invention. By using such inflators, thepressure rise in the passenger compartment resulting from deployment ofthe airbag is kept to a minimum. If the pressure rise is stillexcessive, it is easily vented by the removal of the glass from the rearwindow 493 by suitable means as described below. In this case, eventhough multiple toxic inflators are used, the concentration of toxic gasin the vehicle is quickly reduced as a result of the absence of thewindow 493 and the fact that the inflator gases are hotter than theambient temperature and thus rise to the ceiling and then flow out ofthe broken window 493.

Obviously, although the rear window 493 was chosen for removal, any ofthe side windows could also have been chosen or even a sunroof if one ispresent, and even though a single window was chosen, multiple windowscould also be removed or forcibly broken. In some cases described below,the glass in the window will be broken and in others it will be ejected.If the window is made from tempered glass, it will break into smallharmless pieces that will be ejected from the vehicle due to the higherpressure within the vehicle.

The airbag systems shown in FIG. 61 provide protection of the occupantagainst impacts with various vehicle structural members such as theA-pillar, B-pillar and C-pillar (see the definitions above). Federal lawnow requires protection from impacts with these pillars, which isdifficult to achieve due to the limited space available for padding, andtherefore the law is weak and not very effective. A side impact airbagsuch as 489 coming down from the ceiling can offer excellent protectionfrom impacts with these pillars. For this reason, it will be desirablein many cases to deploy the side airbags when the frontal impact airbagis deployed since a significant number of occupants are still beinginjured in frontal impacts, even though the airbag deployed, by impactswith the A-pillar and the B-pillar.

The airbag systems shown in FIG. 61 include airbags coming out of thesteering wheel, the ceiling and the back of the front seat. It isobvious though that airbag modules can be mounted at other locations inthe passenger compartment such as the lower instrument panel for kneeprotection or the ceiling for driver protection or rear passengerprotection, as described above.

FIGS. 62A, 62B and 62C illustrate various methods by which the glass ina window can be removed, in order to provide for a reduction in thepressure generated in the passenger compartment by the deployment ofairbags as well to enable the exhaust of toxic gases therefrom. In FIG.62A, a fragmented partially schematic cross sectional view of apyrotechnic window breaking mechanism is illustrated generally at 500.It comprises a wire 502 leading from a vehicle crash sensor system shownschematically at 503 and an electric squib, primer or detonator 501which is housed in a housing and is positioned against a portion ofwindow glass 504. When the sensor system 503 determines that the vehicleis experiencing a crash, for which deployment of an airbag is warranted,it sends a signal to the airbag module, not shown, and a separatecircuit also carries a current or other electronic signal to the windowbreaking squib 501 through wire 502. When the squib 501 is ignited asmall but strong shock impulse is transmitted to the glass surface whichis sufficient to shatter the window 504. As noted above, the squibrepresents the entire class of electrically initiated pyrotechnicdevices capable of releasing sufficient energy to cause a vehicle windowto break. Some such devices, for example, use a heated bridge wire whileothers use a semiconductor bridge or a laser initiation system.

In FIG. 62B, an electromechanical window breaking mechanism isillustrated generally at 507 and comprises a housing abutting against aportion of window glass 504. In this embodiment, a current or othersignal from the vehicle crash sensor system 503 releases a spring-loadedimpacting plunger 508 arranged in the housing and having a hardenedsharp tip 509 similar to a machinist's center punch. When the tip 509travels through a release aperture in the housing and impacts the glass504, it causes the glass 504 to shatter. An alternative to theelectrical release of the plunger 508 would be to use a mechanicalsensor which responds to the crash itself. It is well known that aspring-loaded center punch if impinged onto a window of an automobilewill shatter the glass. Their use by vandals and thieves for thispurpose is why their sale to the general public is not permitted, in atleast one state.

Another method for removing the glass from a window is illustrated inFIG. 62C that is a fragmented cross sectional view of a window releasemechanism where the window is completely ejected from the vehicle whenthe pressure in the vehicle exceeds a predetermined design value. Thisvalue is selected such that the window can only be ejected if more thantwo airbags are deployed. In this case, pressure on the surface of theglass 504 creates a force along edges 505 of the glass which is normallypositioned within a mounting structure and retained therein by a gasket506. When that force exceeds the retaining force of the mounting gasket506, the window is released and is ejected by the gas pressure withinthe vehicle.

An alternate method to enable removal of glass during deployment of morethan one airbag as a result of excessive pressure generated within thepassenger compartment by deploying airbags is to design the temper inthe glass so that if the glass is stressed by internal vehicle pressureabove a predetermined amount, the outer surface of the window would beplaced into tension at which point it shatters. The breaking of avehicle window is not a serious condition and in fact it almost alwayshappens in side impact accidents where an airbag is desired. In otherimplementations, not shown, the force created by the pressure on theentire window or door surface is used to deform all or part of amechanism to the point that a spring-loaded impacting pin is released toshatter the window in a similar manner as described above. Other methodswill now be obvious to those skilled in the art.

As discussed above, in addition to providing a release for the excessivepressure associated with the deployment of multiple airbags, a primereason for creating a large opening in the vehicle in the event of anaccident, is to permit the use of propellants other than sodium azidewhereby toxic gases produced by these propellants would be exhaustedfrom the passenger compartment through the broken or removed window. Ifthe passenger compartment of the vehicle is vented, vis-à-vis theaperture created by the shattered or removed glass, nitrocellulose,nitroguanidine, and other double and triple base formulations, tetrazol(see U.S. Pat. No. 4,909,549 to Poole et al.) or similar propellants canbe used for all of the inflators in the airbag system in view of thefact that the passenger compartment is no longer sealed and any toxicgases would be vented out of the passenger compartment. This is not donenow because of the excessive amount of carbon dioxide, and othercontaminants, which are produced and the requirement that the gas in thepassenger compartment be breathable for some set period such as onehour. If one of the above propellants is used in conjunction with aglass shattering or removal system, the size and weight of an inflatorcould be reduced by a factor of two or more and, if efficient aspiratingsystems are also used, an additional factor of about four can beachieved resulting in an inflator which is about one eighth the size ofconventional inflators.

2.4.2 Exhaust Airbag from Vehicle

An alternate method of eliminating the buildup of toxic gas in thepassenger compartment is to exhaust one or more of the airbags out ofthe vehicle as shown in one example in FIG. 63. In this embodiment, thegas in ceiling-mounted airbag 510 is exhausted into a vent 511 locatedin a ceiling 512 of the vehicle. Vent 511 leads outside of the vehicleand thus as the airbag 510 deflates, the gas does not enter the vehiclepassenger compartment where it would be breathed by the occupants. Thistechnique could be used by other airbags which are mounted in the dooror instrument panel. There has been a reluctance to use this techniquefor the front passenger frontal impact protection airbag since thiswould require that a hole be placed in the firewall partially defeatingthe very purpose of the firewall which is to prevent fumes or evenflames from the engine compartment from entering the passengercompartment. This would not be a problem for the ceiling or door-mountedairbags.

As mentioned above, when multiple airbags are deployed in a crash, thesound pressure level becomes excessive to the point that injuries tohuman ear drums can result. To minimize such injuries, airbag systemdesigners have resorted to staging the deployment of the driver andpassenger airbags so that the peak deployment noise pressure is reduced.These systems have the delay circuitry as part of the sensor anddiagnostic circuitry that complicates the design of this circuitry andincreases its cost and reduces the reliability of the system. Analternate and much simpler system is disclosed in FIG. 65A which is adetailed cross sectional view showing the inflator squib incorporating apyrotechnic delay element.

FIG. 65 shows an airbag module 521 having one airbag 520 connectedtherewith, although it is of course possible to have a plurality ofairbags connected to a single module, and the module is connected tosensor and diagnostic circuitry, shown schematically at 531, which sendscurrent or a signal to all of the airbag modules connected thereto whichare to be deployed in a particular crash. As shown in FIG. 65, module520 comprises the airbag 521 and an inflator assembly 522 coupledthereto. The inflator assembly 522 comprises a chamber housing apropellant 523, an initiator 524 coupled through passages in theinflator assembly to the propellant 523 and a squib assembly 525engaging with the initiator 524. The squib assembly 525 is connected tothe sensor and diagnostic circuitry 531 which will determine activationof the squib assembly 525 and thus ignition of the propellant 523 togenerate gas for inflating the airbag 520. The squib assembly 525 isshown in an expanded view in FIG. 65A taken within the circle labeled65A in FIG. 65. The squib assembly 525 comprises a burn-wireelectrically initiated squib 526 and a pyrotechnic delay element 527adjacent thereto. The squib 526 is spaced and isolated from theinitiator 524 by the delay element 527 thereby avoiding prematureinitiation. The delay element 527 is capable of providing any desireddelay from fractions of a millisecond to several milliseconds and issometimes made from a coiled tube containing a propellant or otherpyrotechnic material. Such delay devices are well known to those skilledin the art of designing pyrotechnic delays primarily for military uses.

An alternate mechanical method can be used since pyrotechnic delayelements yielding a few millisecond delay are expensive. One embodimentis illustrated in FIG. 65B which shows a delay producing device wherethe electric squib assembly 525 causes the ignition of a burn-wireelectrically initiated squib 526 which upon ignition releases a firingpin 528. The firing pin 528 is then propelled by a spring 529 through apassage in the squib assembly 525 into a stab primer 530 which initiatesdeployment of the airbag, by means of the activation of the initiator524. The length of travel and the mass of the firing pin 528 can beadjusted to provide the required delay. In the normal position, thesquib 526 retains the firing pin 528 against the expansion force of thespring 529.

The use of aspiration, where the gas to inflate the airbag issubstantially obtained from the passenger compartment itself, is alsodesirable in order to reduce pressure and the amount of toxic gas withinthe passenger compartment of the vehicle. Aspiration systems arecurrently in use for passenger side frontal impact airbag systems, butthe aspiration ratios are quite low. Typically, only about 30% or lessof the gas used to inflate the airbag comes from the passengercompartment with the remainder coming from the burning propellant. Thispercentage can be greatly increased by the careful design of theaspirating nozzle to where as much as about 90% or more of the gas comesfrom the passenger compartment as discussed above. The use of highaspiration ratios also permits the use of hotter gases from the gasgenerator since the vehicle passenger compartment air is used to diluteand thus cool the inflator gases. Thus, in general, the gas from theinflator does not need to be cooled and cooling screens are not needed.Cool gas is also desirable for side thorax and especially headprotection airbags due to the need to keep them inflated for rolloverprotection.

If an airbag is attached to the vehicle ceiling and the inlet from thepassenger compartment into the inflator takes the form of a narrow butlong slit running along the length of the inflator, then an efficientdesign for the nozzle is possible as disclosed herein. In this case, theports that are used for the gas flow from the passenger compartment toenter the airbag can also be used as the exit orifices for the gas toflow out of the airbag during the crash. An additional advantage resultsin this case in that the inflator gases are exhausted high in thepassenger compartment of the vehicle making it even more likely thatthey will flow out of the vehicle through the window which has beenbroken open or removed for that purpose.

This is illustrated in FIG. 66 which is a perspective view of aceiling-mounted airbag system having exit ports at the ceiling level forgas to flow out of the airbag. In FIG. 66, a long thin airbag module 535is positioned in the vehicle ceiling as described herein. When theoccupant presses against an airbag 535 during the crash, pressure buildswithin the airbag 535 causing the gas within the airbag to flow backthrough the module opening 536 and into the passenger compartment 537 atthe ceiling level. Since the exiting gas is hot, it flows out of therear window, not shown, which has been broken or removed, and thus outof the passenger compartment and into the atmosphere. By using theaspirating nozzle as an exit orifice, it is unnecessary to place ventholes within the airbag itself. This is particularly an advantage whenfilm airbags are used.

2.4.3 Blow Out Panel

In some implementations, either due to the geometry of the vehicle, theinability to achieve high aspiration ratios, or the necessity to coolthe inflator gases, breaking of one or more windows may not besufficient to remove enough of the toxic gases to pass the requiredbreath ability tests. The main toxic gas will be carbon dioxide which asit cools will settle in the lower parts of the vehicle. If an occupant,because of unconsciousness or for some other reason, has his mouth belowthe window level, he may be forced to breath an excessive amount of thetoxic gas and be injured. For these cases, it is necessary to create anair passage lower in the vehicle than the possible locations of theoccupant's mouth. One implementation is illustrated in FIG. 66 which isa partial view of the interior of a vehicle showing a blowout panellocated in a low position in the passenger compartment.

As shown in FIG. 66, and in more detail in FIG. 66A, a hole 538 has beenpyrotechnically opened in a location below the seat by shattering afrangible seal in cover 539 by means of a squib 540. The squib 540 isconnected to and initiated by the same sensor and diagnostic circuitrywhich is used as discussed above for breaking the glass in a window.Many other techniques exist for creating an air passage low in thevehicle. In some cases, for example, it might even be desirable to blowopen a vehicle door perhaps 10 seconds after the accident, which may beachieved by appropriate door opening mechanisms (representedschematically in FIG. 66 as 541). This has the added advantage ofhelping to provide egress for injured occupants.

2.4.4 Exhaust Fan

In rare cases, the ventilation provided by breaking a window even withthe addition of a hole in the lower part of the passenger compartment isinsufficient to remove the toxic gas in time to prevent any danger ofinjury to the occupants. When this occurs, a small electrically orpyrotechnically driven fan can be mounted in an opening 542 as shown inFIGS. 66 and 66B. This fan shown at 543 in FIG. 66B which is a partialperspective view of the fan assembly of FIG. 66. In the event of anaccident which requires deployment of more than one airbag, a fan 543powered by the vehicle's electrical system through wires 544 is turnedon for a period of time to pull gas from the lower part of the vehicleforcing it to flow through doors 545. Alternately, the fan 543 can bepowered by its own power supply comprising a battery or capacitor, oreven by a pyrotechnic device.

If the total number of airbags deployed in an accident can be reduced,then the above disclosed methods of removing the toxic gas may not berequired. Therefore, in another preferred embodiment of this invention,each airbag has an associated occupant position sensor to assure thatthere is an occupant present at a particular seating position before theairbags associated with that seating position are deployed. Generally,there would be no reason to deploy an airbag if the seat is unoccupied.More sophisticated versions of occupant position sensors can alsodetermine out-of-position occupants, the presence of a rear facing childseat and children laying on the seat.

In a refinement of this embodiment, more of the electronics associatedwith the airbag system is decentralized and housed within or closelyadjacent to each airbag module. Each module has its own electronicpackage containing a power supply and diagnostic and sometimes also theoccupant sensor electronics. One sensor system is still used to initiatedeployment of all airbags associated with the frontal impact. To avoidthe detrimental noise effects of all airbags deploying at the same time,each module sometimes has its own, preferably pyrotechnic, delay asdiscussed above. The modules for the rear seat, for example, can have aseveral millisecond firing delay compared to the module for the driver,and the front passenger module can have a lesser delay. Each of themodules sometimes also has its own occupant position sensor andassociated electronics. In this configuration, there is a minimumreliance on the transmission of power and data to and from the vehicleelectrical system which is the least reliable part of the airbag system,especially during a crash. Once each of the modules receives a signalfrom the crash sensor system, it is on its own and no longer needseither power or information from the other parts of the system. The maindiagnostics for a module can also reside within the module whichtransmits either a ready or a fault signal to the main monitoringcircuit which now needs only to turn on a warning light if any of themodules either fails to transmit a ready signal or sends a fault signal.

3 Airbags

3.1 Plastic Film Airbags

A fundamental problem with the use of plastic films for airbags is thatwhen a single conventional plastic film is used and a tear is(inadvertently) introduced into the film, the tear typically propagateseasily and the airbag fails catastrophically upon deployment. As notedabove, this invention is concerned with various methods of eliminatingthis problem and thus permitting the use of films for airbags with theresulting substantial cost and space savings as well as a significantreduction in injuries to occupants. The reduction in occupant injuryarises from the fact that the film is much lighter than fabric in aconventional airbag and it is the mass of the airbag traveling at a highvelocity which typically injures the out-of-position occupant. Also,since the packaged airbag is considerably smaller than conventionalairbags, the module is also smaller and the total force exerted on theoccupant by the opening of the deployment door is also smaller furtherreducing the injuries to severely out-of-position occupants caused bythe initial stages of the airbag deployment. Finally, in some preferredimplementations of this invention, the airbag is mounted onto theceiling of the vehicle making it very difficult for an occupant to getinto a position as to be injured by the opening of the deployment door.Ceiling mounting of conventional fabric airbags is less practical duetheir excessive size. Ceiling mounting of full protection film airbags,on the other hand, is practical based on the use of the materials and,the reinforcements disclosed here.

One method of solving the tear problem is to use two film airbags or twoairbag layers, one inside the other, where the airbags or layers areattached to each other with an adhesive which is strong enough to holdthe two airbags or layers closely together but not sufficiently strongto permit a tear in one airbag or layer to propagate to the other. If atear is initiated in the outer airbag or layer, for example, and thematerial cannot support significant tensile stresses in the materialclose to the tear, the inner airbag or layer must accommodate theincreased tensile stress until it can be transferred to the outer layerat some distance from the tear. If the tear is caused by a small hole,this increased stress in the inner bag may only occur for a few holediameters away from the hole. If the inner airbag is also made from anelastomer and the outer airbag layer is made from a less elasticmaterial, the outer material can cause the airbag to take on aparticular, desired shape and the inner airbag is used to provide thetear resistance.

In a preferred embodiment, five layers make up the film that is used toconstruct the airbag. The inner layer is a high tensile strength plasticsuch as NYLON® and the two outer layers are elastomeric and also capableof being heat sealed together. The three layers are joined togetherusing an adhesive layer between each adjacent pair of layers resultingin a total of five layers. In addition to blunting the propagation of acrack, the elastomeric layers allow the airbag to be formed by heatsealing the elastic layers together. Additional layers can be added ifparticular properties are desired. Additional layers may also be used atparticular locations where added strength is desired, such as at theseams. Although five layers are described, a preferred embodiment is touse three layers by eliminating one elastic and one adhesive layer.Also, in many cases, the elastic and inelastic layers can be thermallybonded together eliminating the need for the adhesive layer.

The problem which arises with a two airbag system with one airbag insideof and attached to the other, when both film layers have high elasticmoduli and the cause of the tear in one airbag also causes a tear in thesecond airbag, is solved if one of the materials used for the twoairbags has a low modulus of elasticity, such a thermoplastic elastomer.In this case, even though a tear starts in both airbags at the same timeand place, the tear will not propagate in the thermoplastic elastomerand thus it will also be arrested in the high modulus material a shortdistance from the tear initiation point.

An example of a two layer airbag construction is illustrated in FIG. 71which is a perspective view with portions cut away and removed of a filmairbag made from two layers or sheets of plastic film material, whichare preferably substantially coextensive with one another. Frequently, athird adhesive layer is used if the first and second layers cannot bejoined together.

Some of the constructions discussed below contain various materials forreinforcing films. Although not yet available, a promising product forthis purpose is carbon nanotubes. These materials are 100 times strongerthan steel and have one sixth the weight. Such nanotubes have beendemonstrated at Rice University, The University of Texas and TrinityCollege in Dublin, Ireland.

The phenomenon of crack blunting is discussed in some detail in C.-Y.Hui, A. Jagota, S. J. Bennison and J. D. Londono “Crack blunting and thestrength of soft elastic solids”, Proc. R. Soc. London, A (2003) 459,1489-1516. The invention herein makes use of crack blunting to arrestthe propagation of a crack (or tear) by the use of elastic layers on oneor both sides of the more rigid film, typically NYLON®. The NYLON®prevents the stretching of the elastic films and the elastic films serveto both seal the pieces of plastic film to make an airbag and to bluntthe propagation of cracks or tears.

As discussed above and elsewhere herein, the combination of two layersof film wherein one layer comprises a high tensile strength material,such as biaxially oriented Nylon®, and the other generally thicker layercomprises an elastic material, such as polyurethane or a thermoplasticelastomer, not only provides the high strength plus blunting propertybut also permits the stress concentrations in the seams to besubstantially reduced. This is illustrated in FIG. 72 where 590illustrates an airbag including a high tensile strength layer 590 ofNYLON®, for example, 591 an elastic layer of polyurethane, for example,and the joint 592 illustrates the expansion of the elastic layer 591signifying the redistribution of the stresses in the joint 592. Thisstress distribution takes place both along the seam (i.e., into theplane of the drawing) and into the joint 592 (i.e., from right to leftin the drawing). By this process, the maximum stress can be moved fromthe joint 592 to the material away from the joint 592 where the strengthof the high tensile strength material in layer 590 limits the pressurethat the airbag can withstand. By thereby reducing or eliminating thestress concentrations in the joints 592 and/or seams, the thickness andthus the weight of the material making up the airbag is reduced. Thispermits an airbag to be constructed with interconnected compartmentsformed by joining portions of sheet material together, e.g., by heatsealing or vulcanization, to form the desired shape for occupantprotection while minimizing stress concentrations and thus minimizingthe weight of the airbag.

Appendix 1 (of U.S. patent application Ser. No. 10/817,379) provides afinite element analysis for a production side curtain airbag as used onthe AGM Saturn vehicle. The stresses calculated in the seams are shownto require a NYLON® film thickness of about 0.3 mm or about 0.012 inchesto withstand a gage pressure of about 2.8 kg/cm². Through the use of theelastic film techniques described herein, this thickness can bedramatically reduced to about 0.004 inches or lower.

As mentioned above, U.S. Pat. No. 5,811,506 (Slagel) describes athermoplastic, elastomeric polyurethane for use in making vehicularairbags. Slagel does not mention the possibility of this material foruse in a laminated film airbag. The elasticity of this material and thefact that it can be cast or otherwise made into a thin film renders thisan attractive candidate for this application especially due to its hightemperature resistance and other properties. Such a laminated filmairbag would be considerably thinner and have a lighter weight than thepolyurethane material by itself which would have to be quite thick toavoid becoming a balloon.

Another technique which can be used in some situations where particulargeometries are desired is to selectively deposit or laminate metal foilonto particular sections or locations of the airbag. Such a foil notonly greatly reduces gas permeation or leakage through the material butit also adds local stiffness or tensile strength to a particular area ofthe airbag. This can be used, for example, to reinforce the airbag seamsor joints. The most common material for this purpose is aluminum;however, other metals can also be used. Selective addition of metal foilcan also be used to control the shape of the airbag. For someapplications, one layer of the entire airbag can be foil.

Other additives can be used in conjunction with the film airbagsaccording with this invention including, e.g., aluminum trihydrate orantimony trioxide for flame proofing, BPS by Morton Thiokol for mildewprevention and TINUVUN 765 by Ciba Geigy for ozone resistance.

3.2 Driver Side Airbag

In FIG. 71, the driver airbag is shown in the inflated conditiongenerally at 600 with one film layer 601 lying inside a second filmlayer 602. The film layers 601, 602, or sheets of film laminated orotherwise attached together, are non-perforated and are also referred toas airbags or layers herein since they constitute the same. FIG. 71A isan enlarged view of the material of the inner layer 601 and outer layer602 taken within circle 71A of FIG. 71. When manufactured, the film ofthe inner layer 601 may be made from a thermoplastic elastomer such aspolyurethane, for example, as shown in FIG. 71A, and the outer layer 602may be made from a more rigid material such as NYLON® or polyester. Thetwo film layers 601, 602 are held together along their adjacent regionsby adhesive such as an adhesive 603 applied in a manner sufficient toprovide adherence of the two film layers 601, 602 together, as is knownin the art.

In FIG. 71, a driver side airbag 600 is illustrated where the bag isformed from two flat pieces of material 601, 602 and a centercylindrical piece 604 all of which are joined together using heatsealing with appropriate reinforcement at the heat sealed joints. Heatsealing entails the application of heat to one or both of the surfacesto be joined. In most implementations, the center cylindrical piece 604is not required as taught in U.S. Pat. No. 5,653,464 mentioned above.

The example of FIG. 71 is meant to be illustrative of a generaltechnique to minimize the propagation of tears in a composite filmairbag. In an actual airbag construction, the process can be repeatedseveral times to create a composite airbag composed of several layers,each adjacent pair of layers optionally joined together with adhesive.

The materials used for the various film layers can be the same ordifferent and are generally made from NYLON®, polyethylene or polyester,for the high modulus component and from polyurethane, polyesterelastomer such as HYTREL™ or other thermoplastic elastomers for the lowmodulus component, although other materials could also be used. The useof different materials for the different layers has the advantage thattear propagation and strength properties can complement each other. Forexample, a material which is very strong but tears easily can be used inconjunction with a weaker material which requires a greater elongationbefore the tear propagates or where the tear does not propagate at allas with blunting materials. Alternately, for those cases whereself-shaping is not necessary, all layers can be made from thermoplasticelastomers which expand upon inflation and do not maintain any setshape.

In the implementation of FIG. 71, the adhesive 603 has been applied in auniform coating between the film layers. In some cases, it is preferableto place the adhesive in a pattern so as to permit a tear to propagate asmall distance before the stress is transferred between layers. Thispermits the stress concentration points to move a small distance awayfrom each other in the two films and further reduces the chance that acatastrophic failure will result. Thus, by selecting the pattern of theapplication of the adhesive 603 and/or the location(s) of application ofthe adhesive 603, it is possible to control the propagation of a tear inthe composite airbag 600.

FIG. 71B illustrates an alternate configuration of a composite airbagwhere the outermost airbag 602 has been replaced by a net 605. There maybe additional film layers beneath the inner layer 601 in thisembodiment. A “net” is defined for the purposes of this application asan interlaced or intercrossed network of material, e.g., strips ofmaterial which cross one another. The interlacing may be generated,e.g., by weaving discrete elongate strips of material together or bymolding, casting, progressive coating or a similar process in which casethe material is molded into the network to provide an intercrossedstructure upon formation. Additionally, the net 605 may be formedintegrally with the film material in which case it appears as asubstantial change in material thickness from the net 605 and filmportions of the material to the only film portions of the material. Thestrips of material may be joined at the intersection points in the eventthat discrete material strips are woven together. In the illustratedembodiment, the material strips which constitute the net 605 areoriented in two directions perpendicular to one another. However, it iswithin the scope of the invention to have a net comprising materialstrips oriented in two, non-perpendicular directions (at an angle to oneanother though) or three or more directions so long as the materialstrips are interlaced with each other to form the net. Additionally, thenet pattern can vary from one portion of the airbag to another with theparticular location and orientation determined by analysis to minimizestress concentrations, eliminate wrinkles and folds, or for some otherpurpose. Also, it is understood that the net has openings surrounded bymaterial having a thickness and width substantially smaller than theopenings.

The net 605 may be an integral part of the inner airbag 601 or it can beattached by an adhesive 603, or by another method such as heat sealing,to the inner airbag 601 or it can be left unattached to the inner airbag601 but nevertheless attached to the housing of the airbag system. Inthis case, the stress in the inner airbag 601 is transferred to the net605 which is designed to carry the main stress of the composite airbagand the film of the inner airbag 601 is used mainly to seal and preventthe gas from escaping. Since there is very little stress in the filmlayer constituting the inner airbag 601, a tear will in general notpropagate at all unless there is a failure in the net 605. The net 605in this illustration has a mesh structure with approximately squareopenings of about 0.25 inches. This dimension will vary from design todesign. The adhesive 603 also serves the useful purpose of minimizingthe chance that the net 605 will snag buttons or other objects which maybe worn by an occupant. The design illustrated in FIG. 71B shows the net603 on the outside of the inner airbag 601. Alternately, the net 605 maybe in the inside, internal to the inner airbag 601, especially if it iscreated by variations in thickness of one continuous material.

In one embodiment, the net 605 is attached to the housing of the innerairbag 601 and is designed to enclose a smaller volume than the volumeof the inner airbag 601. In this manner, the inner airbag 601 will berestrained by the net 605 against expansion beyond the volumetriccapacity of the net 605. In this manner, stresses are minimized in thefilm permitting very thin films to be used, and moreover, a film havinga higher elastic modulus can be used. Many other variations arepossible. In one alternative embodiment, for example, the net 605 isplaced between two layers of film so that the outer surface of thecomposite airbag is smooth, i.e., since the film layer is generallysmooth. In another embodiment shown in FIG. 71C, fibers 606 of anelastomer, or other suitable material, are randomly placed and sealedbetween two film layers 601, 602 (possibly in conjunction with theadhesive). In this embodiment, the fibers 606 act to prevent propagationof tears in much the same manner as a net. The net 605 may also beconstructed from fibers.

The driver airbag 600 of FIG. 71 is shown mounted on a vehicle by aconventional mounting structure (not shown) in the driver side positionand inflated in FIG. 71D.

It is understood that the airbag 600 is arranged prior to deployment ina module or more specifically in a housing of the module and furtherthat the interior of the airbag 600 is adapted to be in fluidcommunication with an inflator or inflator system for inflating theairbag, e.g., a gas generation or gas production device. Thus, theinflator is coupled in some manner to the housing. Also, the moduleincludes an initiator or initiation system for initiating the gasgeneration or production device in response to a crash of the vehicle.This structure is for the most part not shown in the drawings but may beincluded in connection with all of the airbag concepts disclosed herein.

An airbag made from plastic film is illustrated in FIG. 73 which is apartial cutaway perspective view of a driver side airbag 610 made fromfilm. This film airbag 610 is constructed from two flat disks or sheetsof film material 611 and 360 which are sealed together by heat weldingor an adhesive to form a seam 613. A hole 617 is provided in one of thesheets 612 for attachment to an inflator (not shown). The hole 617 canbe reinforced with a ring of plastic material 619 and holes 618 areprovided in the ring 619 for attachment to the inflator. A vent hole 615is also provided in the sheet 612 and it can be surrounded by areinforcing plastic disk 616. Since this airbag 610 is formed from flatplastic sheets 611 and 612, an unequal stress distribution occurscausing the customary wrinkles and folds 614.

Several different plastic materials are used to make plastic films forballoons as discussed in U.S. Pat. Nos. 5,188,558, 5,248,275, 5,279,873and 5,295,892. These films are sufficiently inelastic that when two flatdisks of film are joined together at their circumferences and theninflated, they automatically attain a flat ellipsoidal shape. This isthe same principle used herein to make a film airbag, although theparticular film materials selected are different since the material foran airbag has the additional requirement that it cannot fail duringdeployment when punctured.

When the distinction is made herein between an “inelastic” film airbagand an elastic airbag, this difference in properties is manifested inthe ability of the untethered elastic airbag to respond to the pressureforces by becoming approximately spherical with nearly equal thicknessand diameter while the inelastic film airbag retains an approximateellipsoidal shape, or other non-spherical shape in accordance with thedesign of the inelastic film airbag, with a significant differencebetween the thickness and diameter of the airbag.

An analysis of the film airbag shown in FIG. 73 shows that the ratio ofthe thickness to the diameter is approximately 0.6. This ratio can beincreased by using films having greater elasticity. A completely elasticfilm, rubber for example, will form an approximate sphere when inflated.This ratio can also be either increased or decrease by a variety ofgeometric techniques some of which are discussed below. The surprisingfact, however, is that without resorting to complicated tetheringinvolving stitching, stress concentrations, added pieces of reinforcingmaterial, and manufacturing complexity, the airbag made from inelasticfilm automatically provides nearly the desired shape for driver airbagsupon deployment (i.e., the roughly circular shape commonly associatedwith driver side airbags). Note that this airbag still has a less thanoptimum stress distribution which will be addressed below.

Although there are many advantages in making the airbag entirely fromfilm, there is unfortunately reluctance on the part of the automobilemanufacturers to make such a change in airbag design until thereliability of film airbags can be satisfactorily demonstrated. Tobridge this gap, an interim design using a lamination of film and fabricis desirable. Such a design is illustrated in FIG. 74A which is apartial cutaway perspective view of a driver side airbag made from film622 laminated with fabric 621 to produce a hybrid airbag 620. Theremaining reference numbers represent similar parts as in the embodimentshown in FIG. 73. In all other aspects, the hybrid airbag 620 acts as afilm airbag. The inelastic nature of the film 622 causes the hybridairbag 620 to form a proper shape for a driver airbag. The fabric 621,on the other hand, presents the appearance of a conventional airbag whenviewed from the outside. Aside from the lamination process, the fabric621 may be attached to the film 622 directly by suitable adhesives, suchthat there are only two material layers, or by heat sealing or any otherconvenient attachment and bonding method. Note, this is not to beconfused with a neoprene or silicone rubber coated conventional driverside airbag where the coating does not significantly modify theproperties of the fabric.

Analysis, as described in the above-referenced U.S. Pat. No. 5,505,485,has shown that a net is much stronger per unit weight than a fabric forresisting tears. This is illustrated in FIG. 74B which is a partialcutaway perspective view of a driver side airbag 610 made from film 612and a net 622, which is preferably laminated to the film 612 or formedfrom the same material as the film 612 and is integral with it, toproduce a hybrid airbag. The analysis of this system is presented in the'485 patent and therefore will not be reproduced here. The referencenumerals designating the element in FIG. 74B correspond to the sameelements as in FIG. 74A.

For axisymmetric airbag designs such as shown in FIGS. 74A-74D, a moreefficient reinforcement geometry is to place the reinforcements in apattern of circular rings 623 and ribs 625 (FIG. 74C). A cross-sectionalview of the material taken along line 74D-74D in FIG. 74C is shown inFIG. 74D. In this case, the reinforcement has been made by a progressivecoating process from a thermoplastic elastomeric material such aspolyurethane. In this case, the reinforcing rings and ribs 623, 625 aremany times thicker than the spanning thin film portions 624 and thereinforcing ribs 625 have a variable spacing from complete contact atthe center or polar region to several centimeters at the equator. Thereinforcements may comprise the laminated net as discussed above. Sincethe rings and ribs 623, 625 are formed in connection with the innersurface of the airbag 610, the outer surface of the airbag 610 maintainsits generally smooth surface.

In this regard, it should be stated that plastic manufacturing equipmentexists today which is capable of performing this progressive coatingprocess, i.e., forming a multi-layer plastic sheet (also referred to asa material sheet) from a plurality of different plastic layers. One suchmethod is to provide a mold having the inverse form of the predeterminedpattern and apply the specific plastic materials in individual layersinto the mold, all but the initial layer being applied onto apreexisting layer. The mold has depressions having a depth deeper thanthe remaining portions of the mold which will constitute the thickerregions, the thinner portions of the mold constituting the spanningregions between the thicker regions. Also, it is possible and desirableto apply a larger amount of the thermoplastic elastomer in thedepressions in the mold so that the thicker regions will provide areinforcement effect. In certain situations, it is foreseeable that onlythe thermoplastic elastomer can be coated into the depressions whereas aplastic material which will form an inelastic film layer is coated ontothe spanning regions between the depressions as well as in thedepressions in order to obtain an integral bond to the thermoplasticelastomer. The mold can have the form of the polar symmetric patternshown in FIG. 74C.

The film airbag designs illustrated thus far were constructed from flatplastic sheets which have been sealed by heat welding, adhesive orotherwise. An alternate method to fabricate an airbag is to use amolding process to form an airbag 630 as illustrated in FIG. 75A whichis a partial cutaway perspective view of a driver side airbag made fromfilm using blow molding (a known manufacturing process). Blow moldingpermits some thickness variation to be designed into the product, asdoes casting and progressive coating methods molding (other knownmanufacturing processes). In particular, a thicker annular zone 633 isprovided on the circumference of the airbag 630 to give additionalrigidity to the airbag 630 in this area. Additionally, the materialsurrounding the inflator attachment hole 636 has been made thickerremoving the necessity for a separate reinforcement ring of material.Holes 637 are again provided, usually through a secondary operation, forattachment of the airbag 630 to the inflator.

The vent hole 635 is formed by a secondary process and reinforced, or,alternately, provision is made in the inflator for the gases to exhausttherethrough, thereby removing the need for the hole 635 in the bagmaterial itself. Since this design has not been stress optimized, thecustomary wrinkles and folds 634 also appear. The vent hole 635 mightalso be a variable-sized or adjustable vent hole to achieve the benefitsof such as known to those skilled in the art.

One advantage of the use of the blow molding process to manufactureairbags is that the airbag need not be made from flat sheets. Throughcareful analysis, using a finite element program for example, the airbagcan be designed to substantially eliminate the wrinkles and folds seenin the earlier implementations. Such a design is illustrated in FIG. 75Bwhich is a partial cutaway perspective view of a driver side airbag madefrom film using a blow molding process where the airbag design has beenpartially optimized using a finite element airbag model. This design hasa further advantage in that the stresses in the material are now moreuniform permitting the airbag to be manufactured from thinner material.

In some vehicles, and where the decision has been made not to impact thedriver with the airbag (for example if a hybrid airbag is used), theinflated airbag comes too close to the driver if the ratio of thicknessto diameter is 0.6. In these applications, it is necessary to decreasethis ratio to 0.5 or less. For this ratio, thickness means the dimensionof the inflated airbag measured coaxial with the steering column,assuming the airbag is mounted in connection with the steering column,and diameter, or average or effective diameter, is the average diametermeasured in a plane perpendicular to the thickness. This ratio can beobtained without resorting to tethers in the design as illustrated inFIG. 75C which is a side view of a driver side airbag made from filmwhere the ratio of thickness to effective diameter decreases. FIG. 75Dis a view of the airbag of FIG. 75C taken along line 75D-75D. Thisairbag 630 can be manufactured from two sheets of material 631 and 632which are joined together, e.g., by a sealing substrate, to form seal633. Inflator attachment hole 636 can be reinforced with a ring ofplastic material 360 as described above. Many circumferential geometriescan be used to accomplish this reduction in thickness to diameter ratio,or even to increase this ratio if desired. The case illustrated in FIG.75C and FIG. 75D is one preferred example of the use of a finite elementdesign method for an airbag.

Some vehicles have a very steep steering column angle. Direct mountingof an airbag module on the steering wheel will therefore not providegood protection to the driver. One approach to solve this problem can beaccomplished by using a softer wheel rim or column, which adjusts itsangle when pressed by the occupant. However, in some cases this can havejust the opposite effect. If a non-rotating driver side airbag is used,the airbag can be arranged to deploy at a different angle from thesteering wheel without modifying the steering column while the airbagcan be inflated in a direction appropriate for driver protection.Another advantage of using a non-rotating driver side airbag module isthat the angle of the sensor axis is independent of the steering columnangle for self-contained airbag modules.

In a high-speed vehicle crash, the steering column may collapse or shiftdue to the severe crush of the front end of the vehicle. The collapse ofthe steering column can affect the performance of an airbag if the bagis installed on the steering column. One steering system proposed hereinpurposely induces a large stroking of the steering column when thedriver side airbag is activated. This stroking or “disappearing” column,creates a large space in the driver side compartment and thereforeallows the use of a relatively large airbag to achieve betterprotection. In both of the above cases, an airbag module not rotatingwith the steering wheel is the better choice to accomplish occupantprotection.

Recently, there are some developments in steering design, such as“steering by wire”, to eliminate the steering column or the mechanicalmechanism connecting the steering column to the front wheels. Therotation of the steering wheel is converted into a signal which controlsthe turning of front wheels by actuators adjacent to the wheels. Assteer-by-wire is commercialized, it will be advantageous to use theinvention herein of a non-rotating driver side airbag module, which doesnot have to be supported by a steering column.

To provide better viewing to the instrumentation panel for the driver,it is also beneficial to arrange a driver side airbag module so that itdoes not obstruct this view. A non-rotating driver side airbag can beeither arranged to be out of the central portion of the steering wheelor completely out of the steering wheel to avoid this inconvenience.

An inflated airbag 640 interacting with an occupant driver 641 is shownin FIG. 76. Airbag 640 is installed in and deployed from steering wheel642. The steering column 643 has a steep column angle placing the lowerrim 644 of the steering wheel close to the driver 641. When the driver641 moves forward after a crash, the driver's head 645 and the uppertorso 646 make contact with the airbag 640 and the steering wheel 642.The airbag 640 is then deformed and pushed by the occupant 641 so thatthe airbag 640 does not form a cushion between the upper torso 646 andthe steering wheel 642 even though the occupant's driver's head 645 isin full contact with the airbag 640.

A modified column 648 is illustrated in FIG. 77, which is equipped witha joint 647 between a lower part 648A of the steering column 648connected to the vehicle and an upper part 648B of the steering column648 connected to the steering wheel 642. Joint 647 allows the steeringwheel 642 and the inflated airbag 640 to have a variable angle relativeto the lower part 648A of the steering wheel 648 and thus an adjustableangle to the driver 641. Appropriate rotation of the joint 647 enablesthe inflated airbag 640 to align with the head 645 and upper torso 646of the driver 641. The protection offered by the steering column 648including the airbag 640 system in FIG. 77 is an improvement over thesystem in FIG. 76 since the airbag 640 is in a better orientation tocushion the occupant driver 641 and penetration of the lower rim 644 ofthe steering wheel 642 is avoided. The concept of a self-aligned driverside airbag can also be accomplished by rotating the steering wheel 642or utilizing a soft rim for the steering wheel 642.

Construction of the joint 647 may involve use of a pivot hinge havingtwo parts pivotable relative to one another with one part being attachedto the lower part 648A of the steering column 648 and the other partbeing attached to the upper part 648B of the steering column 648.Alternatively, one of the lower and upper parts 648A, 648B can be formedwith a projecting member and the other part formed with a fork-shapedmember and a pivot pin connects the projecting member and fork-shapedmember. Other ways to construct joint 647 will be apparent to thoseskilled in the art in view of the disclosure herein and are encompassedby the description of joint 647.

Pivotal movement of the upper part 648B of the steering column 648 andthus the steering wheel 642 and airbag 640 mounted in connectiontherewith may be realized manually by the driver or automatically by anactuating mechanism. The actuating mechanism can be designed tocooperate with an occupant position and monitoring system to receive thedetected position and/or morphology of the driver 641 and then adjustthe steering wheel 642 to a position within a range of optimum positionsfor a driver in that position and/or with that morphology. To allow forsituations in which the driver manually changes the position of thesteering wheel 642 outside of the range, the actuating mechanism can bedesigned to cooperate with a crash sensor system to receive a signalindicative of an impending or actual crash and then automatically adjustthe position of the upper part 648B of the steering column 648. In thismanner, even if the driver has the steering wheel 642 set in a positionduring regular driving in which it will adversely affect airbagdeployment, the actuating mechanism causes the steering wheel 642 to bere-positioned during the crash

A design with an airbag and an inflator on the steering column isillustrated in FIG. 78. The steering column can comprise an outer shaft651, an inner shaft 652, and a supporting bracket 653. Outer shaft 651can be coupled with the steering wheel 654 at one end region andextended to the engine compartment at the other end region to drive thesteering mechanism 655 which causes turning of the tire(s) of thevehicle. The inner shaft 652 can be coupled with the inflator and airbagmodule 656 at one end region while the other end region can be attachedto a stationary part 657 of the vehicle chassis in the enginecompartment, for example. The supporting bracket 653 can be fixed to thefirewall 658 for support. Bearings 659 and 660 can be placed between thebracket 653 and the outer shaft 651 to rotatably support the outer shaft651 on the bracket 653 and bearings 661 and 662 can be placed betweenthe outer shaft 651 and the inner shaft 652 and can be used forrotatably supporting the outer shaft 651 on the inner shaft 652. Theouter and inner shafts 651, 652 may be tubular and concentric to oneanother.

Inner shaft 652 is stationary, not rotating with the steering wheel 654,therefore the airbag in airbag module 656 can be designed in anarbitrary shape and orientation. For example, a large airbag can bedesigned to provide the optimal protection of the driver. A less rigidsteering wheel or column can also reduce the force exerted on the driverand allow the airbag to align with the driver. For example, the curvedportion 663 of the steering wheel 654 can be designed to be flexible orto move away when the force on the rim of the steering wheel 654 exceedsa certain level. This force can be measured by appropriate measurementdevices or sensors and a processor used to determine when the curvedportion 663 of the steering wheel 654 should be moved away.

Steering wheel 654 can have a central cavity in which the inflator andairbag module 656 is situated. This central cavity may be centered abouta rotation axis of the steering wheel 654.

Although module 656 is referred to as an inflator and airbag module, itis conceivable that only the airbag is arranged in the steering wheel654, i.e., in the cavity defined thereby, while the inflator portion isarranged at another location and the inflation gas is directed into theairbag, e.g., the inflator is arranged on the dashboard and inflatinggas directed into the airbag via a passage in the inner shaft 652.

A driver side restraint system, which is installed on or in thedashboard 675 of a vehicle is depicted in FIG. 79. The inflated airbag671 fills the space between the ceiling of the passenger compartment672, the windshield 673, the steering wheel 674, the dashboard 675, andthe occupant driver 676. The airbag 671 is of such a geometry that theoccupant driver 676 is surrounded by air cushion after the airbag 671 isfully inflated. An additional improvement can be provided if thesteering wheel 674 and column strokes and sinks toward the dashboard 675increasing the space between the occupant driver 676 and the steeringwheel 674. The stroking movement of the steering wheel 674 and columncan be initiated by the restraint system crash sensor. One approach isto use a mechanism where pins 678 lock the column and the steering wheel674. As soon as the sensor triggers to initiate the airbag 671, the pinscan be released and the steering wheel 674 and the column can then movetowards the firewall 677. Other mechanisms for enabling movement of thesteering wheel 674, i.e., the steering column to sink toward thedashboard 675, can be used in the invention.

An airbag 680 installed on the dashboard 681 of a vehicle is illustratedin FIG. 80. The airbag 680 is partially deployed between the windshield682 and the steering wheel 683 and the dashboard 681. The inflator 685provides gas to unfold and inflate the airbag 680. A torsional spring686, or other mechanism, can be used to control the opening of a valve687, which controls the flow of gas out of vent hole 688 of the airbag680. When the pressure inside the airbag 680 is lower than a desiredpressure, the valve 687 can close retaining the gas within the airbag680. When the pressure inside the airbag 680 exceeds a design level, thevalve 687 opens and releases gas from the airbag 680 into the enginecompartment 689, which is separated from the passenger compartment byfirewall 690. Although only a single vent hole 688 and associated valve687 are shown, multiple vent holes and/or valves can be provided.

A distributed inflator and airbag module 691 along the dashboard of avehicle below the windshield 692 is illustrated in FIG. 81A. FIG. 81Billustrates a side view of the inflator and airbag module 691, whichshows the module cover 693, the folded airbag 694, the inflator 695 andthe vent hole 696 covering an opening in the airbag 694. The longtubular inflator 695, which has multiple ports along the module 691, canevenly and quickly generate gas to inflate the airbag 694. Multiple ventholes 696 are shown in FIG. 81A, located near the bottom of thewindshield 692. These vent holes 696, since they cover openings in theairbag 694, can direct, or allow the flow of, the exhaust gases from theairbag 694 into the engine compartment. More specifically, vent holes696 can be used regulate the gas flow from the airbag 694 to the enginecompartment so that the inflated airbag 694 can be matched to theoccupant and the severity of the crash.

Airbag 694 may be attached to the dashboard so that the periphery of theopening in the airbag 694 associated with each vent hole 696 is alignedwith the vent hole 696.

Drive-by-wire is being considered for automobiles. Such a system willpermit a significant reduction in the mass and cost of the steeringwheel and steering column assembly. However, if the airbag is stilldeployed from the steering wheel, the strength and thus weight of theairbag will have to be largely maintained. Thus, a preferablearrangement is to cause the steering wheel and column to move out of theway and have the airbag for the driver deploy from the dashboard or theceiling as discussed elsewhere herein. Such an airbag can bemulti-chambered so as to better capture and hold the driver occupant inposition during the crash.

3.3 Passenger Side Airbag

The discussion above has been limited for the most part to the driverside airbag which is attached to the vehicle steering wheel or otherwisearranged in connection therewith. This technology is also applicable toa passenger side airbag, which is generally attached to the instrumentpanel, as illustrated in FIG. 82 which is a partial cutaway perspectiveview of a passenger side airbag 700 made from three pieces or sheets offlat film 701, 702 and 703 which have joined seams 704 between adjacentpieces of film 701, 702, 703. The passenger side airbag, as well as rearseat airbags and side impact airbags, generally have a different shapethan the driver side airbag but the same inventive aspects describedabove with respect to the driver side airbag could also be used inconnection with passenger side airbags, rear seat airbags and sideimpact airbags. Although illustrated as being constructed from aplurality of sheets of plastic film, the passenger side airbag 700 canalso be made by blow molding or other similar molding process, i.e., asone unitary sheet. Also, for many vehicles, the film sheet 702 isunnecessary and will not be used thereby permitting the airbag to onceagain be manufactured from only two flat sheets. The inflator attachmenthole 706 is now typically rectangular in shape and can be reinforced bya rectangular reinforcement plastic ring 708 having inflator-mountingholes 707. A vent hole 705 can also be provided to vent gases from thedeploying airbag 700. The vent hole 705 might be a variable-sized oradjustable vent hole to achieve the benefits of such as known to thoseskilled in the art.

Another class of airbags that should be mentioned are side impactairbags that deploy from the vehicle seat or door. These also can bemade from plastic film according to the teachings of this invention.

3.4 Inflatable Knee Bolster-Knee Airbag

An example of a knee airbag is illustrated in FIG. 64 which is aperspective view of a knee restraint airbag illustrating the support ofthe driver's knees and also for a sleeping occupant lying on thepassenger seat of the vehicle (not shown). The knee support airbag showngenerally at 514 comprises a film airbag 515 which is composed ofseveral smaller airbags 516, 517, 518, and 519 as disclosed above.Alternately, the knee airbag can be made from a single film airbag asdisclosed in U.S. Pat. No. 5,653,464 referenced above. The knee supportairbag can be much larger than airbags previously used for this purposeand, as a result, offers some protection for an occupant, not shown, whois lying asleep on the vehicle seat prior to the accident.

With the development of the film airbag and the inflator design above, avery thin airbag module becomes possible as disclosed in U.S. Pat. No.5,505,485. Such a module can be made in any length permitting it to beused at many locations within the vehicle. For example, one could bepositioned on the ceiling to protect rear seat occupants. Another onewould stretch the length of the car on each side to protect both frontand rear occupants from head injuries in side impacts. A module of thisdesign lends itself for use as a deployable knee restraint as shown inFIG. 64. Eventually, especially when drive-by-wire systems areimplemented and the steering wheel and column are redesigned oreliminated, such an airbag system will be mounted on the ceiling andused for the protection of all of the front seat passengers and driverin frontal impacts. With the economies described above, airbags of thistype will be very inexpensive, perhaps one-fifth the cost of currentairbag modules offering similar protection.

In FIG. 83, a knee protection airbag for the front driver is showngenerally at 709 (and is also referred to as a knee bolster herein).Since the knee airbag 709 fills the entire space between the knees andthe instrument panel and since the instrument panel is now located at asubstantial distance from the occupant's knees, there is substantiallymore deflection or stroke provided for absorbing the energy of theoccupant. Submarining is still prevented by inflating the knee airbag709 to a higher pressure, typically in excess of 1 bar and sometimes inexcess of 2 bars gage, and applying the force to the occupant kneesbefore he or she has moved significantly. Since the distance ofdeployment of the knee airbag 709 can be designed large enough to belimited only by the interaction with an occupant or some other object,the knee airbag 709 can be designed so that it will inflate until itfills the void below the upper airbag, not illustrated in this figure.The knee protection airbag 709 can take the form of a fabric or any ofthe composite airbags disclosed above, e.g., include a plastic filmlayer and an overlying net, or two or more plastic film layers, usuallyat least one is inelastic to provide the shape of the knee bolster andat least one is elastic to control the propagation of a tear. The kneebolster airbag can also be deployed using as aspirated inflator or othermethod permitting the airbag to be self-limiting or self-adjusting so asto fill the space between the knees of the occupant and the vehiclestructure. In FIG. 83, the width of the cells is typically less than thewidth of the knee of an occupant. In this manner, the capturing of theknees of the occupant to prevent them from sliding off of the kneeairbag 709 is enhanced.

In preferred designs presented herein and below, the knee airbag 709 isdeployed as a cellular airbag with the cells, frequently in the form oftubes, interconnected during inflation and, in most cases, individualvalves in each chamber close to limit the flow of gas out of the chamberduring the accident. In this manner, the occupant is held in positionand prevented from submarining. A composite film is one preferredmaterial, however, fabric can also be used with some increased injuryrisk. The cellular or tubular airbags designs described herein are alsosometimes referred as compartmentalized airbags.

Normally, the knee bolster airbag will not have vents. It will bedeployed to its design pressure and remain deployed for the duration ofthe accident. For some applications, a vent hole will be used to limitthe peak force on the knees of the occupant. As an alternate toproviding a fixed vent hole as illustrated in the previous examples, avariable vent hole can be provided as shown in FIGS. 100 and 100A(discussed below). Alternately, this variable vent function can beincorporated within the inflator as described in U.S. Pat. No.5,772,238.

Typically, inflatable knee bolster installations comprise an inflatableairbag sandwiched between a rigid or semi-rigid load distributing impactsurface and a reaction surface. When the inflator is triggered, theairbag expands to move the impact surface a predetermined distance to anactive position. This position may be determined by tethers between thereaction and impact surfaces. These installations comprise numerousparts, bits and pieces and require careful installation. In contrast, ina preferred knee bolster described herein, there is no rigid loaddistributing surface but rather, the knee bolster conforms to the shapeof the knees of the occupant. Tethers in general are not required orused as the shaping properties of inelastic films are utilized toachieve the desired airbag shape. Finally, preferred designs herein arenot composed of numerous parts and in general do not require carefulinstallation. One significant problem with the use of load distributionplates as is commonly done in the art is that no provision is made tocapture the knees and thus, especially if the crash is an angular impactor if the occupant is sitting on an angle with respect to the kneebolster or has his or her legs crossed, there is a tendency for theknees to slip sideways off of the knee bolster defeating the purpose ofthe system. In the multi-cellular knee bolster disclosed herein, thecells expand until they envelop the occupant's knees, capturing them andpreventing them from moving sideways. Once each cell is filled to adesign pressure, a one-way valve closes and flow out of the cell isprevented for the duration of the crash. This design is especiallyeffective when used with an anticipatory sensor as the knees can becaptured prior to occupant movement relative to the passengercompartment caused by the crash. A signal from the anticipatory sensorwould initiate an inflator to inflate the knee bolster prior to orsimultaneous with the crash.

An improvement to this design, not illustrated, is to surround theairbags with a net or other envelope that can slide on the surface ofthe airbag cells until they are completely inflated. Then, when theoccupant begins loading the airbag cells during the crash, displacementof the knees not only compresses the cells that are directly in linewith the knees but also the adjacent cells thus providing a significantincrease to the available effective piston area to support the knees inmuch the same way that a load distribution plate functions. Such a netor envelope effectively distributes the load over a number of cells thuslimiting the required initial pressure within the airbag cells. Othermethods of accomplishing this load distribution include the addition ofsomewhat flexible stiffeners into the surface of the airbag where itcontacts the knees, again with the goal of causing a load on one cell tobe partially transferred to the adjacent cells.

In a preferred design, as discussed below, the cellular airbags inflateso as to engulf the occupant by substantially filling up all of thespace between the occupant and the walls of the passenger compartmentfreezing the occupant in his or her pre-crash position and preventingthe occupant from ever obtaining a significant velocity relative to thepassenger compartment. This will limit the acceleration on the occupantto below about 15-20 Gs for a severe 30 MPH barrier crash. This retainsthe femur loads well below the requirements of FMVSS-208 and canessentially eliminate all significant injury to the occupant in such acrash. This, of course, assumes that the vehicle passenger compartmentis effectively designed to minimize intrusion, for example.

In most of the preferred designs disclosed herein, the surface thatimpacts the occupant is a soft plastic film and inflicts little if anyinjury upon impact with the occupant. Even the fabric versions when usedas a knee bolster, for example, can be considered a soft surfacecompared with the load distribution plates or members that impact theknees of the occupant in conventional inflatable knee bolster designs.This soft impact is further enhanced when an anticipatory sensor is usedand the airbags are deployed prior to the accident as the deploymentvelocity can be substantially reduced.

In a conventional airbag module, when the inflator is initiated, gaspressure begins to rise in the airbag which begins to press on thedeployment door. When sufficient force is present, the door breaks openalong certain well-defined weakened seams permitting the airbag toemerge from its compartment. The pressure in the airbag when the dooropens, about 10 to 20 psi, is appropriate for propelling the airbagoutward toward the occupant, the velocity of which is limited by themass of the airbag. In the case of a film airbag, this mass issubstantially less, perhaps by as much as a factor of three or more,causing it to deploy at a much higher velocity if subjected to thesehigh pressures. This will place unnecessary stresses in the material andthe rapid movement of the airbag past the deployment door could induceabrasion and tearing of the film by the deployment door. A film airbag,therefore, must be initially deployed at a substantially lower pressure.However, conventional deployment doors require a higher pressure toopen. This problem is discussed in detail in the above-referencedpatents and patent applications where, in one implementation, apyrotechnic system is used to cut open the door according to theteachings of Barnes et al. (U.S. Pat. No. 5,390,950).

There are of course many ways of making inflatable knee restraints usingchambered airbags, such as illustrated in U.S. Pat. No. 6,685,217,without deviating from the teachings of this invention.

3.5 Ceiling Deployed Airbags

Airbags disclosed herein and in the assignee's prior patents arebelieved to be the first examples of multi-chambered airbags that aredeployed from the ceiling and the first examples of the use of tubularor cellular airbags. These designs should become more widely used asprotection is sought for other situations such as preventing occupantsfrom impacting with each other and when developments in drive-by-wireare implemented. In the former case, airbags will be interposed betweenseating positions and in the latter case, steering wheel assemblies willbecome weaker and unable to support the loads imposed by airbags. Insome cases, in additional to support from the ceiling, these airbagswill sometimes be attached to other surfaces in the vehicle such as theA, B and C pillars in much the way that some curtain airbags now receivesuch support.

One method of forming a film airbag is illustrated generally at 710 inFIG. 84. In this implementation, the airbag is formed from two flatsheets or layers of film material 711, 712 which have been sealed, e.g.,by heat or adhesive, at joints 714 to form long tubular shapedmini-airbags 713 (also referred to herein as compartments or cells) inmuch the same way that an air mattress is formed. In FIG. 84, a singlelayer of mini-airbags 713 is shown. It should be understood that themini-airbags 713 are interconnected to one another to allow theinflating gas to pass through all of the interior volume of the airbag710. Also, the joints 714 are formed by joining together selected,opposed parts of the sheets of film material 711, 712 along parallellines whereby the mini-airbags 713 are thus substantially straight andadjacent one another. In other implementations, two or more layers couldbe used. Also, although a tubular pattern has been illustrated, otherpatterns are also possible such as concentric circles, waffle-shaped orone made from rectangles, or one made from a combination of thesegeometries or others. The film airbag 710 may be used as either a sideairbag extending substantially along the entire side of the vehicle, anairbag disposed down the center of the vehicle between the right andleft seating positions or as a rear seat airbag extending from one sideof the vehicle to the other behind the front seat (see FIG. 85) and mayor may not include any of the venting arrangements described herein.

FIG. 85 is a perspective view with portions removed of a vehicle havingseveral deployed film airbags. Specifically, a single film airbag havingseveral interconnected sections, not shown, spans the left side of thevehicle and is deployed downward before being filled so that it fitsbetween the front seat and the vehicle side upon inflation (an airbagspanning the right side of the vehicle can of course be provided). Thisprovides substantial support for the airbag and helps prevent theoccupant from being ejected from the vehicle even when the side windowglass has broken. A system which also purports to prevent ejection isdescribed in Bark (U.S. Pat. No. 5,322,322 and U.S. Pat. No. 5,480,181).The Bark system uses a small diameter tubular airbag stretchingdiagonally across the door window. Such a device lacks the energyabsorbing advantages of a vented airbag however vents are usually notdesired for rollover protecting airbags. In fact, the device can act asa spring and can cause the head of the occupant to rebound and actuallyexperience a higher velocity change than that of the vehicle. This cancause severe neck injury in high velocity crashes. The airbag of Bark'322 also is designed to protect primarily the head of the occupant,offering little protection for the other body parts. In contrast to thecompletely sealed airbag of Bark, a film airbag of the present inventioncan have energy absorbing vents and thus dampens the motion of theoccupant's head and other body parts upon impact with the film airbag.Note that the desirability of vents typically goes away whenanticipatory sensors are used as discussed elsewhere herein.

The airbag of Bark '322 covers the entire vehicle opening and receivessupport from the vehicle structure, e.g., it extends from one side ofthe B-pillar to the other so that the B-pillar supports the airbag 720.In contrast to the tube of Bark, the support for a preferred embodimentof the invention disclosed herein in some cases may not requirecomplicated mounting apparatus going around the vehicle door and downthe A-pillar but is only mounted to or in the ceiling above the sidedoor(s). Also, by giving support to the entire body and adjusting thepressure between the body parts, the airbag of the present inventionminimizes the force on the neck of the occupant and thus minimizes neckinjuries.

3.5.1 Side Curtain Airbags

In FIG. 85, a single side protection airbag for the driver side isillustrated at 720. A single front airbag spans the front seat forprotection in frontal impacts and is illustrated at 723 with the ceilingmounted inflator at 724. A single airbag is also used for protection ofeach of the rear seat occupants in frontal impacts and is illustrated at725. With respect to the positioning of the side airbag 720, the airbag720 is contained within a housing 722 which can be position entirelyabove the window of the side doors, i.e., no portion of it extends downthe A-pillar or the B-pillar of the vehicle (as in Bark '322). The sideairbag housing 722 thus includes a mounting structure (not shown) formounting it above the window to the ceiling of the vehicle and such thatit extends across both side doors (when present in a four-door vehicle)and thus protects the occupants sitting on that side of the vehicle fromimpacting against the windows in the side doors. To ensure adequateprotection for the occupants from side impacts, as well as frontalimpacts and roll-overs which would result in sideward movement of theoccupants against the side doors, the airbag housing 722 is constructedso that the airbag 720 is initially projected in a downward directionfrom the ceiling prior to inflation and extends at least substantiallyalong the entire side of the ceiling. This initial projection may bedesigned as a property of the module 722 which houses the airbag 720,e.g., by appropriate construction and design of the module and itscomponents such as the dimensioning the module's deployment door anddeployment mechanism.

Although a variety of airbag designs can be used as the side impactprotection airbag, one preferred implementation is when the airbagincludes first and second attached non-perforated sheets of film and atear propagation arresting mechanism arranged in connection with each ofthe film sheets for arresting the propagation of a tear therein. A netmay also be used as described above. The net would constrict or tensionthe airbag if it were to be designed to retain an interior volume lessthan the volume of the airbag (as discussed above).

The airbag can include a venting device (e.g., a venting aperture asshown in FIGS. 74A and 74B) arranged in connection with the airbag forventing the airbag after inflation thereof. In certain embodiments, theairbag is arranged to extend at least along a front portion of theceiling such that the airbag upon inflation is interposed between apassenger in the front seat of the vehicle and the dashboard (thisaspect being discussed below with respect to FIG. 89).

FIG. 86 is a view looking toward the rear of the vehicle of the deployedside protection airbag of FIG. 85. An airbag vent is illustrated as afixed opening 721. Other venting designs are possible including ventingthrough the airbag inflator as disclosed in the above-referenced patentsand patent applications as well as the variable vent described belowwith reference to FIGS. 100 and 100A or even no vent for rolloverprotection.

The upper edge of the airbag is connected to an inflator 722 and thatthe airbag 720 covers the height of the window in the door in thisimplementation.

FIG. 86A is a view of a side airbag similar to the one of FIG. 86although with a different preferred shape, with the airbag 720 removedfrom the vehicle. The parallel compartments or cells can be seen. Thisaspect is discussed below with reference to FIGS. 94-96.

3.5.2 Frontal Curtain Airbags

FIGS. 87 and 88-88D illustrate the teachings of this invention appliedin a manner similar to the airbag system of Ohm in U.S. Pat. No.5,322,326. The airbag of Ohm is a small limited protection systemdesigned for the aftermarket. It uses a small compressed gas inflatorand an unvented thin airbag which prevents the occupant from contactingwith the steering wheel but acts as a spring causing the occupants headto rebound from the airbag with a high velocity. The system of FIG. 87improves the performance of and greatly simplifies the Ohm design byincorporating the sensor and compressed gas inflator into the samemounting assembly which contains the airbag. The system is illustratedgenerally at 730 in FIG. 87 where the mounting of the system in thevehicle is similar to that of Ohm.

In FIG. 88, the module assembly is illustrated from a view lookingtoward the rear of the airbag module of FIG. 87 with the vehicleremoved, taken at 88-88 of FIG. 87. The module 730 incorporates amounting plate 731, a high pressure small diameter tube constituting aninflator 733 and containing endcaps 734 which are illustrated here ashaving a partial spherical surface but may also be made from flatcircular plates. The mounting plate 731 is attached to the vehicle usingscrews, not illustrated, through mounting holes 735. An arming pin 729is illustrated and is used as described below.

FIG. 88A is a cross sectional view of the airbag module of FIG. 88 takenat 88A-88A and illustrates the inflator initiation system of thisinvention. The inflator 733 is illustrated as a cylindrical tube,although other cross sectional shapes can be used, which contains a hole730 therein into which is welded by weld 732 to an initiation assembly737. This assembly 737 has a rupture disk 738 welded into one end. Arupture pin 739 is positioned adjacent rupture disk 738 which will bepropelled to impact the rupture disk 738 in the event of an accident asdescribed below. When disk 738 is impacted by pin 739, it fails therebyopening essentially all of the orifice covered by disk 738 permittingthe high pressure gas which is in a tube of the inflator 733 to flow outof the tube 733 into cavity 740 of initiator assembly 737 and thenthrough holes 741 into cavity 742. Cavity 742 is sealed by the airbag736 which now deploys due to the pressure from the gas in cavity 742.

When the vehicle experiences a crash of sufficient severity to requiredeployment of the airbag 736, sensing mass 743, shown in phantom, beginsmoving to the left in the drawing toward the front of the vehicle.Sensing mass 743 is attached to shaft 744 which in turn is attached toD-shaft 745 (see FIG. 88C). As mass 743 moves toward the front of thevehicle, D-shaft 745 is caused to rotate. Firing pin 747 is held andprevented from moving by edge 746 of D-shaft 745. However, when D-shaft745 rotates sufficiently, edge 746 rotates out of the path of firing pin747 which is then propelled by spring 748 causing the firing pin pointto impact with primer 749 causing primer 749 to produce high pressuregas which propels pin 739 to impact disk 738 releasing the gas frominflator tube 733 inflating the airbag 736 as described above. Thesensor 743,744, D-shaft 745 and primer mechanism 747, 748, 749 aresimilar to mechanisms described in U.S. Pat. No. 5,842,716.

FIG. 88B is a cross sectional view, with portions cutaway and removed,of the airbag module 730 of FIG. 88 taken at 88B-88B and illustrates thearming pin 729 which is removed after the module 730 is mounted onto thevehicle. If the module 730 were to be dropped accidentally without thisarming pin 729, the sensor could interpret the acceleration from animpact with the floor, for example, as if it were a crash and deploy theairbag 736. The arming system prevents this from happening by preventingthe sensing mass 743 from rotating until the arming pin 729 is removed.

FIG. 89 is a perspective view of another preferred embodiment of theairbag of this invention 720 shown mounted in a manner to provideprotection for a front and a rear seat occupant in side impactcollisions and to provide protection against impacts to the roof supportpillars in angular frontal impacts and to offer some additionalprotection against ejection of the occupant.

More particularly, in this embodiment, an airbag system for protectingat least the front-seated occupant comprises a single integral airbag720 having a frontal portion 726 sized and shaped for deploying in frontof the front-seated occupant and a side portion 727 sized and shaped fordeploying to the side of the front-seated occupant. In this manner,airbag 720 wraps around the front-seated occupant during deployment forcontinuous front to side coverage. An inflator (not shown) is providedfor inflating the single integral airbag with gas. As shown, the sideportion 727 may be sized and shaped to deploy along an entire side ofthe vehicle, the side portion 727 is longer than the frontal portion 726and the frontal portion 726 and side portion 727 are generally orientedat a 90 degree angle relative to each other. As with the other sidecurtain airbags discussed in connection with FIGS. 85, 86, 86A and 89,the airbag 720 may be housed in the ceiling. Also, as noted throughoutthis application, airbag 720 may comprise one or more sheets of film andthe tear propagation arresting structure or a net may be provided totension or constrict the deployment of the airbag 720. The constructioncan also comprise straight or curved interconnected cells or tubularstructures.

FIGS. 90 and 91 illustrate another embodiment of the invention intendedto provide protection from side impacts and rollover accidents not onlyfor a person in the front seat of a motor vehicle such as a motor car,but also for a person in the rear seat of the vehicle which is similarto that shown in FIGS. 85, 86 and 86A.

Referring to FIG. 90, the housing 715 is provided over both the frontdoor 716 and the rear door 750. The airbag or other type of inflatableelement 751 is shown in the inflated state in FIG. 91. The inflatableelement 751 has its top edge 752 secured to a part of the housing 715 orceiling of the passenger compartment that extends above the doors 716,750 of the motor vehicle (see, e.g., FIG. 86A). The design of theinflatable element is similar to that shown in FIG. 84 or 86A, with theinflatable element including a plurality of parallel cells orcompartments 752, which when inflated are substantially cylindrical. Agas generator 750 is provided which is connected to the inflatableelement 751 in such a way that when the gas generator 750 is activatedby a sensor 751 to supply gas to the cells 752. Sensor 751 may beseparate as shown or formed integrally with the gas generator 750, orwhich is otherwise associated with the gas generator 750, and respondsto a crash condition requiring deployment of the inflatable element 751to activate the gas generator 750. Thus, as the inflatable element 751inflates, the cells 752 inflate in a downward direction until theinflatable element 751 extends across the windows in the doors 716, 750of the motor vehicle (see FIG. 86). As the inflatable element 751inflates, the length of the lower edge thereof decreases by as much as30% as a consequence of the inflation of the cells 752. This reductionin the length of the lower edge ensures that the inflated element 751 isretained in position as illustrated in FIG. 91 after it has beeninflated. Although shown as parallel tubes, other geometries are ofcourse possible such as illustrated in FIGS. 98A-98L.

The inflatable element 751 described above incorporates a plurality ofparallel substantially vertical, substantially cylindrical cells 752.The inflatable element 751 may be made of interwoven sections of amaterial such as film or other material such as woven fabric. Such ainterweaving of material comprises a first layer that defines the frontof the inflatable element 751, i.e., the part that is visible in FIGS.90 and 91, and a second layer that defines the back part, i.e., the partthat is adjacent the window in FIGS. 90 and 91, whereby selected partsof the first region and the second region are interwoven to define linksin the form of lines where the front part and the back part of theinflatable element are secured together. A technique for making aninflatable element of inter-woven sections of material is described inInternational Patent Publication No. WO 90/09295.

The tubes or cells 752 can be further joined together as illustrated inFIG. 92A by any method such as through the use of an additional sheet ofmaterial 753 which joins the front and back edges 754 and 755 of theadjacent cells 752 in order to render the inflatable element 751 moreresistant to impacts from parts of the body of an occupant. Theadditional chambers 756 formed between the additional sheet of material753 and the front and back edges of the cells 752 can either bepressurized at the same pressure as the tubes or cells 752 or they canbe left exposed to the atmosphere, as is preferred. Although illustratedas joining adjacent cells of the inflatable element 751, they canalternatively be arranged to join non-adjacent cells. Although the cellsare illustrated as parallel tubes, any geometry of chambers, cells ortubes can benefit from this improvement including those as illustratedin FIGS. 98A-98L.

FIG. 92 is a cross section showing the nature of the cells 752 of theinflatable element 751 of FIGS. 90 and 91. It can be seen that the cells752 are immediately adjacent to each other and are only separated bynarrow regions where the section of material, e.g., film, forming thefront part of the inflatable element 751 has been woven or otherwiseattached by heat sealing or adhesive with the section of materialforming the back part of the inflated element.

Also, as noted throughout this application, inflatable element 751 mayhave any of the disclosed airbag constructions. For example, inflatableelement 751 may comprise one or more sheets of film and the tearpropagation arresting mechanism or a net may be provided to tension orconstrict the deployment of the inflatable element 751. The film surfacefacing the occupant need not be the same as the film facing the sidewindow, for example. In order to prevent broken glass, for example, fromcutting the airbag, a thicker film, a lamination of a film and a fabricor a film and a net can be used.

There are of course many ways of making ceiling-mounted frontalprotection airbags using chambers without departing from the teachingsof this invention such as disclosed in published patent applicationsWO03093069, 20030234523 and 20030218319. Such airbags can be made fromtubular sections or sections of other shapes and the amount ofdeployment of such airbags can be determined by occupant sensors asdisclosed in other patents assigned to the assignee of this patent. Suchairbags can be flat as disclosed herein or other shapes.

3.5.3 Other Compartmentalized Airbags

As mentioned above, anticipatory crash sensors based on patternrecognition technology are disclosed in several of assignee's patentsand pending patent applications. The technology now exists based onresearch by the assignee to permit the identification and relativevelocity determination to be made for virtually any airbag-requiredaccident prior to the accident occurring. This achievement now allowsairbags to be reliably deployed prior to the accident. The implicationsof this are significant. Prior to this achievement, the airbag systemhad to wait until an accident started before a determination could bemade whether to deploy one or more of the airbags. The result is thatthe occupants, especially if unbelted, would frequently achieve asignificant velocity relative to the vehicle passenger compartmentbefore the airbags began to interact with the occupant and reduce his orher relative velocity. This would frequently subject the occupant tohigh accelerations, in some cases in excess of 40 Gs, and in many casesresulted in serious injury or death to the occupant especially if he orshe is unrestrained by a seatbelt or airbag. On the other hand, avehicle typically undergoes less than a maximum of 20 Gs during even themost severe crashes. Most occupants can withstand 20 Gs with little orno injury. Thus, as taught herein, if the accident severity could beforecast prior to impact and the vehicle filled with plastic filmairbags that freeze the occupants in their pre-crash positions, thenmany lives will be saved and many injuries will be avoided.

One scenario is to use a camera, or radar-based or terahertz-basedanticipatory sensor to estimate velocity and profile of impactingobject. From the profile or image, an identification of the class ofimpacting object can be made and a determination made of where theobject will likely strike the vehicle. Knowing the stiffness of theengagement part of the vehicle allows a calculation of the mass of theimpacting object based on an assumption of the stiffness impactingobject. Since the impacting velocity is known and the acceleration ofthe vehicle can be determined, we know the impacting mass and thereforewe know the severity or ultimate velocity change of the accident. Fromthis, the average chest acceleration that can be used to just bring theoccupant to the velocity of the passenger compartment during the crashcan be calculated and therefore the parameters of the airbag system canbe set to provide that optimum chest acceleration. By putting anaccelerometer on the airbag surface that contacts the occupant, theactual chest acceleration can be measured and the vent size can beadjusted to maintain the calculated optimum value. With this system,neither crush zone or occupant sensors are required, thus simplifyingand reducing the cost of the system and providing optimum results evenwithout initiating the airbag prior to the start of the crash.

There is of course a concern that if the airbags are inflated too early,the driver may lose control of the vehicle and the accident would bemore severe than in the absence of such early inflation. To put thisinto perspective, experiments and calculations show that a reasonablemaximum time period to inflate enough airbags to entirely fill a normalsedan is less than 200 ms. To protect the occupants of such a vehicle byfilling the vehicle with airbags before the accident would requireinitiating deployment of the airbags about 200 ms prior to the accidentwhich corresponds to a distance of vehicle travel of approximately 15feet for the case where two vehicles are approaching each other with aclosing velocity of about 60 MPH. It is unlikely that any action takenby the driver during that period would change the outcome of theaccident and when the sensor signals that the airbags should bedeployed, a control system can take control of the vehicle and preventany unstable motions.

FIG. 93 illustrates one preferred method of substantially filling thepassenger compartment with airbags. Primary airbag 760 along withsecondary airbags 761, 762, and 763 prior to inflation are attached toone or more aspirated inflators 776 and stored, for example, within theheadliner or ceiling of the vehicle. When the anticipatory or othercrash sensor, not shown, determines that deployment is necessary,primary airbag 760 deploys first and then secondary airbags 761-763deploy from gas that flows through airbag 760 and through one-way valves764. Inflation continues until pressure builds inside the airbags760-763 indicating that they have substantially filled the availablevolume. This pressure buildup reduces and eventually stops theaspiration and the remainder of the gas from the gas generator flowseither into the airbags 760-763 to increase their pressure or into thepassenger compartment. Since the pumping ratio of the aspiratedinflators 776 is typically above 4, approximately 75% of the gas in theairbags 760-763 comes from the passenger compartment thus minimizing thepressure increase in the passenger compartment and injuries to the earsof the occupants. This also permits the substantial filling of thepassenger compartment without the risk of breaking windows or poppingdoors open. If additional pressure relief is required then it can beachieved, for example, by practicing the teachings of U.S. Pat. No.6,179,326.

In a similar manner, primary airbag 765 inflates filling secondaryairbags 766-770 through one-way valves 771. Additionally, airbags 775mounted above the heads of occupants along with secondary airbags 772can be inflated using associated inflators 776 to protect the heads ofthe occupants from impact with the vehicle roof or headliner. Ifoccupant sensors are present in the vehicle, then when the rear seat(s)is (are) unoccupied, deployment of the rear-seat located airbags can besuppressed.

The knees and lower extremities of the occupants can be protected byknee airbags 780 and secondary airbags 779 in a similar manner. Thedesign of these airbags will depend on whether there is a steering wheel774 present and the design of the steering wheel 774. In some cases, forexample, a primarily airbag may deploy from the steering wheel 774 whilein other cases, when drive-by-wire is implemented, a mechanism may bepresent to move the steering wheel 774 out of the way permitting thesecondary airbag(s) 779 to be deployed in conjunction with the kneeairbag 780. The knee airbag deployment will be discussed in more detailbelow.

FIG. 93A illustrates a view from the top of the vehicle with the roofremoved taken along line 93A-93A in FIG. 93 with the vehicle unoccupied.As can be seen, primary airbag 760, for example, is actually a row oftubular structures similar to that shown in FIG. 84. Additionally,curtain airbags 786 are present only in this implementation and theyalso comprise several rows of tubes designed to contact the occupantsand hold them away from contacting the sides of the vehicle. Airbags 787are also advantageously provided down the center of the vehicle tofurther restrain the occupants and prevent adjacent occupants fromimpacting each other.

In the preferred design, support for the airbags relies of substantiallyfilling the vehicle and therefore loads are transferred to the walls ofthe vehicle passenger compartment. In many cases, this ideal cannot becompletely achieved and straps of tethers will be required to maintainthe airbags in their preferred locations. Again, this will depend of thedesign and implementation of this invention to a particular vehicle.

The particular designs of FIGS. 93 and 93A are for illustrative purposesonly and the particular method of substantially filling a portion of thepassenger compartment with airbags will depend substantially on thevehicle design.

An alternate design is illustrated in FIG. 94 where a cellular airbag790 deploys from the steering wheel in a somewhat conventional mannerand additional lateral tubes 791 deploy between the occupant and thewindshield. These airbags also provide added support for the steeringwheel airbag for those cases where drive-by-wire has been implementedand the heavy structural steering wheel and column has been replaced bya lighter structure.

FIG. 95 illustrates an example wherein cellular tubular airbags madefrom thin plastic film, for example, expand is a flower pattern toengage the occupants and receive support from the walls, ceiling etc. ofthe passenger compartment. The airbags deform and interact with eachother and the occupants to conform to the available space and to freezethe occupants in their pre-crash positions. Airbags 792 come from theceiling for upper body protection. Airbags 793 deploy from the upperinstrument panel for upper body protection and airbags 794 deploy forlower body protection. Airbags 795 protect the knees and lowerextremities and airbags 796 protect the rear seated occupants. Finally,airbags 797 again provide protection for the tops of the heads of theoccupants. Although not shown in this drawing, additional airbags may beprovided to prevent the lateral movement of the occupants such ascurtain and center-mounted airbags. Again, the intent is to fill as muchof the vehicle passenger compartment surrounding the occupant aspossible. If occupant sensors are present and the absence of arear-seated occupant, for example, can be detected, then the rear seatairbags need not be deployed.

FIGS. 96 and 96A illustrate an example of a flower-type airbag design.The inflator 800, preferably an aspirated inflator, discharges into acommon distribution volume or manifold, which can be made from theplastic film, which distributes the gas to the cells or tubes 802 of theairbag assembly through one-way valves 804, formed in the sheet of thetubes 802, in a manner similar to the tubular airbags of FIG. 93. Anenvelope 803 of plastic film is provided to contain the tubes 802.Alternately, the tubes 802 can be connected together along theiradjacent edges and the envelope 803 eliminated.

FIGS. 97 and 97A illustrate an example of a knee bolster airbag 805 andits inflation sequence. Only four tubes are illustrated althoughfrequently, a larger number will be used. The inflation gas comes fromthe inflator, not shown, into a manifold 807 which distributes the gasinto the tubes 806 through one-way valves 808 formed in the material ofthe airbag 805. During inflation, the airbag 805 unrolls in a mannersimilar to a Chinese whistle.

In some of the implementations illustrated here, the airbags do not havevent holes. At the end of the crash, the gas in the airbags should beallowed to exhaust, which generally will occur through the inflatorhousing. Vents in the airbags for the purpose of dissipating the kineticenergy of the occupants can, in many cases, be eliminated since thephilosophy is to freeze the occupant before he or she has achievedsignificant velocity relative to the passenger compartment. In otherwords, there will be no “second collision”, the term used to describethe injury producing impact of the occupant with the walls of thepassenger compartment. The occupants will, in general, experience thesame average deceleration as the vehicle which in a 30 mph barrier crashis significantly less than 20 Gs.

FIGS. 98A, 98D, 98F, 98H, 98J and 98L illustrate six related prior artcurtain airbag designs that have been modified according to teachings ofthis invention to include the use of an envelope or a material sheetthat spans the cells or tubes that make up the curtain airbag. Thecurtain airbag of FIG. 98A, designated 810, is a design based onparallel vertical tubes 811 and can be made from fabric or plastic film.Sheets of fabric or film material 812 are attached to the outer edges oftubes 811 so as to span from one tube to the adjacent tubes asillustrates in FIG. 98B which is a view of FIG. 98A taken along line98B-98B. The volumes created between the tubes 811, i.e., cells, can bepressurized as illustrated in FIG. 98C or left exposed to the atmosphereas illustrated in FIG. 98B. The particular geometry that the cells willacquire is shown simplified here. In reality, the cell geometry willdepend on the relative lengths of the various material sections, thethickness of the material and the relative inflation pressures of eachcell. Care must be exercised in the design to assure that resultingairbag will fold properly into the storage area. The presence of theenvelope of spanning sheets renders the curtain airbag 810 significantlymore resistant to deformation on impact from the head of the occupant,for example. This improves the ability of the airbag to retain theoccupant's head within the vehicle during a side impact or rollover. Themain function of the curtain airbag 810 is to prevent this partialejection which is the major cause of injury and death in side impact androllover accidents. Although the envelope or spanning sheets 812 addadditional material to the airbag 810, the added stiffness createdactually permits the use of thinner materials for the entire airbag 810and thus reduces the total weight and hence the cost of the airbag 810.

FIGS. 98D and 98E illustrate an alternate geometry of a side curtainairbag where the tubes acquire a varying thickness and shape. Curtainairbag 813 has tubes 814 and an envelope or spanning sheet 815. FIGS.98F and 98G illustrate still another geometry of a side curtain airbagwhere the tubes 817 are formed by joining islands between the opposingsheets of material. As in all of the cases of FIGS. 98A, 98D, 98F, 98H,98J and 98L, various manufacturing processes can be used to join theopposing sheets of material including sewing, heat sealing, adhesivesealing and interweaving where the entire bag is made in one passthrough the loom, among others. Curtain airbag 816 has tubes 817 and anenvelope or spanning sheet 818 (FIGS. 98F and 98G).

FIGS. 98H and 981 illustrate another geometry of a side curtain airbagwhere the tubes again acquire a roughly rectangular shape. Curtainairbag 819 has tubes 820 and an envelope or spanning sheet 821. FIGS.98J and 98K illustrate yet another alternate geometry of a side curtainairbag where the tubes are slanted but still retain a roughlyrectangular shape. Curtain airbag 822 has tubes 823 and an envelope orspanning sheet 824.

Finally, FIGS. 98L and 98M illustrate still another geometry of a sidecurtain airbag where the tubes again acquire a roughly rectangular shapewith the tubes running roughly fore and aft in the vehicle. Curtainairbag 825 has tubes 826 and an envelope or spanning sheet 827.

Deployment of an airbag from the vehicle trim such as the headliner,A-Pillar, B-Pillar, C-Pillar was believed to be first disclosed in thecurrent assignee's patents referenced above. As airbags begin to fillmore and more of the passenger compartment as taught here and in otherpatents to the current assignee, the edges of the passenger compartmentor the locations where the walls of the passenger compartment joinbecome attractive locations for the deployment of airbags. This isespecially the case when the airbags are made from thin plastic filmthat can be stored at such locations since they occupy a minimum ofspace. Thus, storage locations such as disclosed in U.S. PatentApplication Publication No. 20030178821 are contemplated by this andprevious inventions by the current assignee. For some applications, itis possible to put the entire airbag system in the headliner if kneeprotection is not required. This is a problem for convertible vehicleswhere the edges of the passenger compartment become more important.

The size of the cells or tubes in the various airbag designs discussedabove can vary according to the needs of the particular application. Fora given internal pressure, the thickness of the film material decreasesas the diameter of the tubes decreases. Since the thickness determinesthe weight of the airbag and thus the potential to cause injury onimpact with an occupant, in general, an airbag made from multiplesmaller tubes will cause less injury than a single-chambered airbag ofthe same size. Therefore, when possible the designs should use moresmaller cells or tubes. In the extreme, the vehicle can be filled with alarge number of small airbags each measuring three inches or less indiameter, for example, and as long as the passenger compartment issubstantially filled at least between the occupant and the compartmentin the direction of the crash, the exact positioning of a particularairbag becomes less important as each one will receive support fromothers and eventually the passenger compartment walls.

Through the implementation of the ideas expressed herein, the airbagsystem becomes truly friendly. It can deploy prior to the accident,freeze the occupant in his or her pre-crash position, impact theoccupant without causing injury, and gradually deflate after theaccident. Inflators would preferably be aspirated to draw most of therequired gas from the passenger compartment. Since an aspirated inflatorautomatically adjusts to provide just the right amount of gas, onlysingle stage pyrotechnic systems would be required. Occupant sensorswould not be necessary as the system would adjust to all occupantsregardless of whether they were seated in a rear-facing child seat,belted, unbelted, out-of-position, lying down, sleeping, had their feetin the dashboard, etc. By eliminating the dual stage inflator, usingaspiration thereby greatly reduces the amount of propellant required andby using thin plastic film, this airbag system is not only by far thebest performing system it is also potentially the least expensivesystem.

In FIG. 99, the advantages of the self-limiting airbag system disclosedherein and in U.S. Pat. No. 5,772,238 and with reference to FIG. 85,when used with a rear-facing child seat, are illustrated. In this case,where multiple film airbags are illustrated, the airbags deploy but thedeployment process stops when each of the film airbags interacts withthe child seat and the pressure within each bag rises to where the flowis stopped. In this case, the child 666 is surrounded by airbags 664 andfurther protected from the accident rather than being injured as is thecase with current design airbags. The airbags 664 can be additionallysurrounded by a net or other envelope 665 most of which has been cutawayand removed in the figure. In other implementations, a single airbagwill be used in place of the multiple airbags illustrated here ormultiple attached airbags can be used eliminating the need for the net.

The self-limiting feature is illustrated here by either a variableorifice exhaust port in the airbag, discussed in more detail below, or,preferably, provision is made in the airbag inflator itself asillustrated in the referenced '238 patent where a close-down of theaspiration system is used during the deployment portion of the processand a smaller variable orifice is used during the deflation portion. Theaspiration cutoff can be designed so that the airbag deploys until thepressure begins to rise within the bag which then stops the inflationprocess, closes the aspiration ports and the airbag then becomes stifferto absorb the kinetic energy of the impacting occupant. Thus, during thedeployment phase, very little force is exerted on the occupant, or thechild seat, but as the occupant begins to move into and load the airbag,substantial force is provided to limit his or her motion.

3.6 Rear of Seat Mounted Airbags

FIG. 95, discussed above, illustrates airbags that deploy from the rearof the front seat to protect rear seat occupants of a vehicle in acrash. These airbags also provide protection for front seat occupants tohelp prevent unbelted occupants in the rear seat from moving into thefront seat during a crash and causing injury to those occupants seatedin the front seat.

3.7 Exterior Airbags

Airbags that deploy outside of the vehicle have been disclosed primarilyfor side impact in the current assignee's patents. Generally, theseexternally deployed airbags are based on the use of an anticipatorysensor that identifies that an accident is about to occur using, forexample, pattern recognition technologies such as neural network.Normally, these airbags are made from fabric but as the properties offilms improve, these fabric airbags will be replaced by film airbags. Inparticular, using technology available today, the combination of a filmand a reinforcing net can now be used to construct externally deployedairbags that are both stronger and lighter in weight than fabric. U.S.Patent Publication No. 20030159875 discloses the use of a resin for apedestrian protection airbag. All of the film airbag constructionsillustrated herein for interior use are also applicable for external usewith appropriate changes in dimensions, material properties etc. asneeded to satisfy the requirements of a particular application.

Particular mention should be made of pedestrian protection since this israpidly becoming a critical safety issue primarily in Japan and Europewhere the percentage of people killed in automobile accidents that arepedestrians is greater than in North America. Although many patents havenow issued and are pending relating to pedestrian airbags, none, exceptthose of the current assignee, are believed to make use of ananticipatory sensor that can identify that the vehicle is about toimpact with a pedestrian. See, e.g., U.S. Patent Publication No.20030159875 and EP01338483A2. Since this technology has been developedby the current assignee, the technology is now available to identifythat a pedestrian is about to be struck by the vehicle. This technologyuses a camera or other imaging system and a pattern recognition systemsuch as a neural network or combination network as defined in theabove-referenced current assignee's patents.

Exterior airbags can require a substantial amount of gas for inflationand thus are candidates for aspirated inflators such as disclosed inU.S. Patent Application Publication No. 20020101067 and above herein.Exterior airbags can get quite large and thus require a substantialamount of gas. Also they frequently require a high pressure. Aspiratedinflators can economically satisfy both of these requirements. Suchexterior airbags can also be of the shape and construction as disclosedherein and illustrated, for example, in U.S. Patent ApplicationPublication No. 20040011581. Such exterior airbags can be made fromplastic film.

3.8 Variable Vent

A great deal of effort has gone into the design on “smart” inflatorsthat can vary the amount of gas in the airbag to try to adjust for theseverity of the crash. The most common solution is the dual stage airbagwhere either of two charges or both can be initiated and the timingbetween the initiation can be controlled depending on the crash.Typically, one charge is set off for low speed crashes and two forhigher speed crashes. The problem, of course, is to determine theseverity of the crash and this is typically done by a passengercompartment-mounted crash sensor. This is relatively easy to do forbarrier crashes but the crashes in the real world are quite different.For example, some pole crashes can appear to be mild at the beginningand suddenly become severe as the penetrating pole strikes the engine.In this case, there may not be time to initiate the second charge. Analternate solution, as reported in current assignee's patents listedabove, is to use a single stage inflator but to control the flow of gasinto and/or out of the airbag. If this is an aspirated inflator, thiscontrol happens automatically and if the airbag is a film airbag, it canbe designed to interact with any occupant and thus inflator control isnot required.

In an alternate situation where either a conventional inflator is usedor an aspirated inflator is used, the flow out of the airbag can bemanaged to control the acceleration of the chest of the occupant. Mostairbags have a fixed vent hole. As an alternate to providing a fixedvent hole as illustrated in the previous examples, a variable vent holecan be provided as shown in FIGS. 100 and 100A, where FIG. 100 is apartial cutaway perspective view of a driver side airbag made from filmhaving a variable vent in the seam of the airbag. In this embodiment ofan airbag, a hinged elastic member or flap 835 is biased so that ittends to maintain vent 830 in a closed position. As pressure riseswithin the airbag, the vent 830 is forced open as shown in FIG. 100 andFIG. 100A, which is a detail of the vent 830 shown in FIG. 100 takenalong line 100A-100A of FIG. 100. This construction enables the use of asmaller inflator and also reduces the maximum chest acceleration of theoccupant in a crash and more accurately controls the deceleration of theoccupant. In FIGS. 100 and 100A, vent 830 contains an opening 833 formedbetween film layer 834 and reinforcement member 832. Film layer 831 isalso sealed to reinforcing member 832. Member 835 is attached toreinforcing member 832 (via portion 837) through film 834. A weakenedsection 836 is formed in member 835 to act as a hinge. The elasticity ofthe material, which may be either metal or fiber reinforced plastic orother suitable material, is used to provide the biasing force tending tohold the variable opening closed. The variable vent can also beaccomplished through controlling the flow back through the inflatorassembly. This latter method is particularly useful when aspiratedinflators and self limiting airbags are used. For other variable ventdesigns, see the discussion about FIGS. 103-112.

FIG. 101 shows a typical chest G pulse experienced by an occupant andthe resulting occupant motion when impacting an airbag during a 35-MPHfrontal impact in a small vehicle. When the variable orifice airbag isused in place of the conventional airbag, the chest acceleration curveis limited and takes the shape similar to a simulation result shown inFIG. 102. Since it is the magnitude of the chest acceleration thatinjures the occupant, the injury potential of the airbag in FIG. 102 issubstantially less than that of FIG. 101.

Since the variable exhaust orifice remains closed as long as thepressure in the airbag remains below the set value, the inflator needonly produce sufficient gas to fill the airbag once. This isapproximately half of a gas which is currently produced by standardinflators. Thus, the use of a variable orifice significantly reduces thetotal gas requirement and therefore the size, cost and weight of theinflator. Similarly, since the total amount of gas produced by allinflators in the vehicle is cut approximately in half, the total amountof contaminants and irritants is similarly reduced or alternately eachinflator used with the variable orifice airbag is now permitted to besomewhat dirtier than current inflators without exceeding the totalquantity of contaminants in the environment. This in turn, permits theinflator to be operated with less filtering, thus reducing the size andcost of the inflator. The pressure buildup in the vehicle is alsosubstantially reduced protecting the occupants from ear injuries andpermitting more or larger airbags to be deployed.

Characteristics of inflators vary significantly with temperature. Thus,the mass flow rate of gas into the airbag similarly is a significantfunction of the temperature of the inflator. In conventional fixedorifice airbags, the gas begins flowing out of the airbag as soon aspositive pressure is achieved. Thus, the average pressure in the airbagsimilarly varies significantly with temperature. The use of a variableorifice system as taught by this invention however permits the bags tobe inflated to the same pressure regardless of the temperature of theinflator. Thus, the airbag system will perform essentially the samewhether operated at cold or hot temperature, removing one of the mostsignificant variables in airbag performance. The airbag of thisinvention provides a system which will function essentially the same atboth cold and hot temperatures.

The variable orifice airbag similarly solves the dual impact problemwhere the first impact is sufficient to trigger the crash sensors in amarginal crash where the occupant is wearing a seatbelt and does notinteract with the airbag. A short time later in a subsequent, moreserious accident, the airbag will still be available to protect theoccupant. In conventional airbags using a fixed orifice, the gasgenerator may have stopped producing gas and the airbag may have becomedeflated.

Since the total area available for exhausting gas from the airbag can besubstantially larger in the variable orifice airbag, a certain amount ofprotection for the out-of-position occupant is achieved even when theaspiration system of the referenced '238 patent is not used. If theoccupant is close to the airbag when it deploys, the pressure will beginto build rapidly in the airbag. Since there is insufficient time for thegas to be exhausted through the fixed orifices, this high pressureresults in high accelerations on the occupant's chest and can causeinjury. In the variable orifice embodiment, however, the pressure willreach a certain maximum in the airbag and then the valve would open toexhaust the gas as fast as the gas generator is pumping gas into theairbag thus maintaining a constant and lower pressure than in the formercase. The airbag must be sufficiently deployed for the valve to beuncovered so that it can operate. Alternately, the valving system can beplaced in the inflator and caused to open even before the cover opensthereby handling the case where the occupant is already against thedeployment door when the airbag deployment is initiated.

Many geometries can be used to achieve a variable orifice in an airbag.These include very crude systems such as slits placed in the bag inplace of round exhaust vents, rubber patches containing one or moreholes which are sewn into the bag such that the hole diameter getslarger as the rubber stretches in response to pressure in the bag, plusa whole variety of flapper valves similar to that disclosed herein. Slitsystems, however, have not worked well in experiments and rubber patchesare affected by temperature and thus are suitable only for very crudesystems. Similarly, the bag itself could be made from a knittedmaterial, which has the property that its porosity is a function of thepressure in the bag. Thus, once again, the total amount of gas flowingthrough the bag becomes a function of the pressure in the bag.

Although the case where the pressure is essentially maintained constantin the bag through the opening of a valve has been illustrated, it ispossible that for some applications, a different function of thepressure in the bag may be desirable. Thus, a combination of a fixedorifice and variable valve might be desirable. The purpose of adjustingthe opening area of an airbag vent hole is to control the gas flow rateout of the vent hole according to the pressure inside the airbag. If thepressure is higher, then the area of the vent hole becomes larger andallows more gas to flow out. By regulating the pressure inside anairbag, the force applied on an occupant is minimized.

A superior solution to the problem is to place an acceleration sensor onthe surface to the airbag that contacts the chest of the occupant, or isexpected to contact the chest of the occupant or the forwardmost part ofthe occupant. An electronic controlled valve can then be coupled to theaccelerometer and the acceleration of the chest of the occupant can becontrolled to limit this acceleration below some value such as 40 Gs.Alternately, if the severity of the crash has been accurately forecast,then the airbag can provide the minimum deceleration to the occupant'schest to bring the occupant to the same speed as the vehicle passengercompartment at the time the airbag has become deflated.

When airbags are used in conjunction with an anticipatory sensor toinflate and hold occupants in their pre-crash position, they usuallywill not have vents for dissipating the kinetic energy of the occupantssince the occupants will never attain a significant velocity relative tothe vehicle. Usually, it will be desirable to retain such airbags intheir inflated state for several seconds and then to deflate them topermit the occupants to egress from the vehicle. There are severalmethods of permitting such airbags to deflate including: opening theaspiration vent when aspirated inflators are used; electrically and/ormechanically opening the airbags when the pressure drops belowatmospheric pressure; chemically, thermally melting or burning orotherwise opening a hole in such an airbag after a predetermined timeperiod or perhaps two seconds (for example) after the vehicle motion hasstopped; etc.

3.8.1 Discharge Valves for Airbags

FIG. 103 shows an airbag 841 equipped with a discharge valve 842 inaccordance with a first embodiment of the invention. The discharge valve842 is interposed between the gas-filled interior of the airbag and anatmosphere exterior of the airbag 841 so as to enable gas or other fluidfrom the airbag to the outlet from the interior of the airbag to theexterior atmosphere. Discharge valve 842 is situated separate and apartfrom an opening in the airbag 841 through which gas flows into theinterior of the airbag 841.

The airbag 841 may be any airbag arranged on or in a vehicle, includingbut not limited to, a frontal airbag, a side airbag, a knee bolster andan externally deployed airbag.

As shown in FIG. 103A, discharge valve 842 comprises a fixed, bottomplate 843 arranged in connection with or associated with the airbag 841,e.g., on an outer layer of the material of the airbag or arranged inconjunction with the inflator, and has a pattern of openings. Bottomplate 843 may overlie one or more openings in the airbag 841. A topplate 844 is arranged over the bottom plate 843 and is movable relativeto the bottom plate 843. Top plate 844 has the same pattern of openingsas the bottom plate 843. Top plate 844 is mounted to a fix component inthe vehicle by a spring 845 to allow for movement relative to the bottomplate 843 to thereby vary the correspondence between the openings in thetop plate 844 and the bottom plate 843.

When the phrase “pattern of openings” is used to refer to thearrangement of openings in the bottom plate 843 and top plate 844, itmust be understood that the openings are not required to be arranged inany discernible or specific geometric pattern. Rather, the pattern maysimply be the overall arrangement of the openings.

Gas from the airbag 841 flows through the openings in the bottom plate843 and then through the openings in the top plate 844 with the volumeand/or flow rate of the gas being determined by the degree ofcorrespondence between the openings in the top plate 843 and theopenings in the bottom plate 843. That is, in a maximum gas outflowposition, the top plate 844 will be in a position so that openings inthe top plate 844 correspond exactly with the openings in the bottomplate 843. On the other hand, in a minimum gas outflow position, the topplate 843 will be in a position so that the openings in the top plate843 will over lie solid portions of the bottom plate 843. Any positionbetween these extreme positions is also possible so that the gas outflowrate is controlled by the variable position of the top plate 843relative to the bottom plate 843.

A movement mechanism is provided to move the top plate 843 relative tothe bottom plate 843 and is generally effective to move the top plate843 to multiple positions relative to the bottom plate 843 and forvariable, adjustable durations. That is, the top plate 843 can be movedfrom one position to another position during the discharge of gas fromthe airbag 841 to vary the outflow of gas during the discharge. Movementof the top plate 843 and timing of the movement of the top plate 843 maybe controlled by an appropriate control system to obtain the desiredoutflow rate, duration and/or volume of gas from the airbag 841. Thecontrol system can be designed to consider the properties of theoccupant to be protected by the airbag 841, e.g., the occupant'sposition, morphology, type and identification.

One embodiment of the movement mechanism comprises a piezoelectricbi-morph crystal arrangement 18 which shakes the top plate 843 back andforth (in the direction of arrow A) to thereby modulate the valveopenings defined by the openings in the bottom plate 843 and top plate843. The piezo-electric crystal 846 is driven by a drive signal andassociated electronics 847. The electronics 847 can be connected to orincorporated into a vehicle occupant sensor capable of determining anoptimum discharge rate of the airbag 841 so that the top plate 843 ismoved to achieve the optimum discharge rate.

Another movement mechanism could be an inductive actuator or motorarrangement with a cam offset (represented by motor 847A in FIG. 103B).In this case, the motion could be started during a pre-crash period andengaged with a magnetic clutch or piezoelectric clutch thereafter. Amotor can also be used which is offset by the pitch of the openings andthereby achieve the possibility of regulating the valve openings definedby the openings in the top plate 843 and fixed plate 843.

Referring now to FIG. 104, another embodiment of a discharge valve isshown designated generally as 848. In this embodiment, an indent orgroove 849 is formed in a metal foil diaphragm 850 in a peripheralsurface of the airbag 841 (see FIG. 104A), or in a surface against whichthe pressure in the airbag 841 is effective. A signal is fed to acircuit formed by the groove 849 so that there is a large impedance(I²R) drop across the groove that melts the metal foil and therebyweakens the diaphragm 850. The pressure of the gas in the airbag 841will then cause the weakened region to break and open a passage betweenthe interior of the airbag 841 and the exterior. A 12 V firing signalmay be preferably used.

Several grooves can be provided on the metal foil diaphragm 850 toenable different size openings to be formed. Instead of metal foil, thediaphragm may be made of any material which melts upon the formation ofan electric circuit. The grooves 849 can be annular and concentric.

When multiple annular grooves or rings 849 are provided, with anassociated circuit formed for each groove 849, a signal can be sent to aparticular circuit to cause an opening having a pre-determined size tobe formed, i.e., the weakened region will be at a set diameter from acenter of the diaphragm 850. In this manner, a logic input can be usedto determine what size opening is needed to provide for a controlled,appropriate discharge and then generate a signal to cause the annulargroove 849 which will provide for that size opening to weaken andsubsequently break upon exertion of the pressure from the gas in theairbag 841.

Referring now to FIGS. 105 and 105A, another embodiment of a dischargevalve is shown. In this embodiment, the discharge valve 851 comprises anelastomer diaphragm 852 with apertures 853 therein. In a rest condition,the diaphragm 852 is flat and the apertures 853 are relatively small.However, when pressure is applied, the diaphragm 852 expands to thecondition shown in FIG. 105 and the apertures 853 become larger. Gasfrom the interior of the airbag 841 flows to the exterior through theenlarged apertures 853. The expansion of the diaphragm 852 depends onthe magnitude of the pressure of the gas in the airbag 841.

The edges of the diaphragm 852 are preferably fixed relative to theairbag 841 and may even be attached to the airbag 841. For example, theedges of the diaphragm 852 may be attached to the outer material layerof the airbag 841.

Control of the flow rate and/or volume of gas from the airbag 841 can beachieved through appropriate determination of the size and/or number ofthe apertures 853.

The material from which the diaphragm 852 is made is preferablypre-stretched and then die cut. Instead of an elastomer, other resilientand/or flexible materials may be used.

Referring now to FIGS. 106, 106A and 106B, in this embodiment, adischarge valve for an airbag is represented generally as 854. Thedischarge valve includes a fixed aperture disk 855 arranged inconnection with or associated with the airbag 841 and a movable aperturedisk 856 mounted over the fixed disk 855. Fixed disk 855 may overlie oneor more openings in the airbag 841. Movable disk 856 has alternatingsolid sections 857 and open sections 858 and is connected to an arm 859.The center of disk 856 is mounted through the fixed disk 855 by amounting pin 860, although this mounting arrangement can be eliminatedand other devices for mounting the movable disk 856 relative to thefixed disk 855 employed in the invention. Arm 859 is associated with arotation mechanism 861 to enable the arm 859 to be moved in thedirections of arrow B. Movement of the arm 859 results in movement ofthe movable disk 856 relative to the fixed disk 855 so that thecorrespondence between the apertures in the fixed disk 855 and theapertures in the movable disk 856 is varied (to thereby adjust valveopenings defined by the apertures in the fixed disk 855 and movable disk856). This variation enables the discharge flow to be controlled.

The rotation mechanism 861 may be a solenoid, bi-morph piezoelectricelement, ferromagnetic arrangement or drive, ferroelectric arrangementor drive or a thermal-based arrangement, e.g., a phase change metal.That is, almost any type of controllable mechanism for moving the arm859 can be used in the invention. When a solenoid is used, applicationof alternating electrical current causes forward and reverse motions ofthe arm 859.

FIGS. 107, 107A and 107B show another embodiment of a discharge valve inaccordance with the invention and is designated generally as 862.Discharge valve 862 includes a valve seat 863 formed in connection withor associated with the airbag 841 and arranged to enable flow of gasfrom the interior of the airbag 841 therethrough. Valve scat 863 mayoverlie one or more openings in the airbag 841. A valve member 864engages with the valve 863 and a valve spring 865 is arranged to providea biasing force to press the valve member 864 toward the airbag 841 toclose the opening(s) formed by the valve scat 863 and valve member 864.

FIGS. 108, 108A and 108B show another embodiment of a discharge valvefor an airbag in accordance with the invention and is designatedgenerally as 866. Discharge valve 866 includes a substrate 867 havingthree or more spiral cuts 868 arranged to form cantilevered arms 869that will deflect under pressure. The cantilevered arms 869 may be diecut into the material of the airbag 841. Multiple spiral arms thus forma plurality of springs. In operation, the pressure of the gas in theinterior of the airbag 841 will urge the arms 869 upward as shown inFIG. 108 thereby opening the cuts to form passages at the locations ofthe cuts 868.

Instead of die cutting the cantilevered arms 869 into the material ofthe airbag 841, a dedicated diaphragm may be provided in connection withan outer material layer of the airbag 841 and cuts made in thisdiaphragm.

FIGS. 109, 109A and 109B show another embodiment of a discharge valvefor an airbag in accordance with the invention and is designatedgenerally as 870. Discharge valve 870 includes a substrate 871 cut in aspecific manner to define a square cantilevered spring matrix having acentral region 872 and cantilevered arms 873 that will deflect underpressure. The cantilevered arms 873 may be die cut into the material ofthe airbag 841. Multiple spiral arms thus form a large spring valve. Inoperation, the pressure of the gas in the interior of the airbag 841will urge the arms 86 upward as shown in FIG. 109 thereby raising thecentral region 872 and opening passages between the interior of theairbag 841 and the exterior.

Instead of die cutting the cantilevered arms 873 into the material ofthe airbag 841, a dedicated diaphragm may be provided in connection withan outer material layer of the airbag 841 and cuts made in thisdiaphragm.

Referring now to FIGS. 110A and 110B, instead of plates having a patternof openings interposed between the airbag interior and airbag exterior,a pair of cylinders could be used.

As shown in FIGS. 110A and 110B, an inner cylinder 874 has a pattern ofopenings and is positionable inside an outer cylinder 875 such that thepattern of openings in the outer cylinder 875 are in alignment with thepattern of openings in the inner cylinder 874. Outer cylinder 875 iscoupled to a motor 876 or other actuating device for moving the outercylinder 875 in a stroked manner in the direction of arrow A, in whichcase, the outer cylinder 875 is moved up and down relative to the innercylinder 874 (FIG. 8A). The pattern of openings in the inner cylinder874 may completely align with the pattern of openings in the outercylinder 875 when the outer cylinder 875 is fully in the up position.

The motor 876 is controlled by a gas discharge rate determination unit880, e.g., a processor containing an algorithm relating the desired gasdischarge rate to the required action of the motor 876 to move the outercylinder 875 to provide for the desired gas discharge rate. Such analgorithm may be determined experimentally or empirically. The gas ratedetermination unit 880 is provided with or determines the desired gasdischarge rate through input from a detection unit 881 which detects,measures or determines the morphology of the occupant to be protected bythe airbag, the type of occupant, the identification of the occupant,the position of the occupant and/or the severity of the crash. Any ofthese factors, or combinations of these factors, may be used in thedetermination of the discharge rate to optimally protect the occupant ina crash. The discharge rate determination unit 880 and detection unit881 may be used in any of the embodiments described herein.

As shown in FIG. 110B, a motor or other actuating device 876 may rotatethe outer cylinder 875 in the direction of arrow B relative to the innercylinder 874, in which case, the inner cylinder 875 is situated withinthe outer cylinder 875. The openings in the outer cylinder 875 may alignfully with the openings in the inner cylinder 874 (in which case thevalve is in the full discharge position) or align with material betweenthe openings in the inner cylinder 874 (in which case the valve is inthe full blocked-discharge position). Between these extreme positions isa wide range of variations in the discharge of the gas in the airbag.

Instead of having the outer cylinder 875 move relative to the innercylinder 874, the reverse situation could also be used, i.e., move theinner cylinder relative to the stationary outer cylinder, in which case,the outer cylinder would be fixed to the airbag since the stationarycylinder is preferably fixed to the airbag. Also, as shown, the airbaginterior is on the side of the outer cylinder 875 and the airbagexterior is on the side of the inner cylinder 874 so that gas isdischarged from the airbag first through the openings in the outercylinder 875 and then through the openings in the inner cylinder 874.The reverse situation could also be used. Thus, in general, the set ofopenings of one cylinder is in flow communication with the interior ofthe airbag and the set of openings in the other cylinder is in flowcommunication with the exterior of the airbag so that the degree ofregistration or alignment between the openings determines the dischargerate of gas from the airbag.

Referring now to FIGS. 111A and 111B, instead of plates or cylindershaving a pattern of openings interposed between the airbag interior andairbag exterior, a pair of cones could be used.

As shown in FIGS. 111A and 111B, an inner cone 878 has a pattern ofopenings and is positionable inside an outer cone 877. Inner cone 878 iscoupled to a motor 879 or other actuating device for moving the innercone 878 in a stroked manner in the direction of arrow A, in which case,the inner cone 878 is moved up and down relative to the outer cone 877(FIG. 111A). The pattern of openings in the inner cone 878 maycompletely align with the pattern of openings in the outer cone 96 whenthe inner cone 878 is fully in the up position.

In the alternative, as shown in FIG. 111B, the motor or other actuatingdevice 876 may rotate the inner cone 878 in the direction of arrow Brelative to the outer cone 877, in which case, the inner cone 878 issituated almost entirely within the outer cone 877. The openings in theinner cone 878 may align fully with the openings in the outer cone 877(in which case the valve is in the full discharge position) or alignwith material between the openings in the outer cone 877 (in which casethe valve is in the full blocked-discharge position). Between theseextreme positions is a wide range of variations in the discharge.

Instead of having the inner cone 878 move relative to the outer cone877, the reverse situation could also be used, i.e., have the outer conemove relative to the inner cone, in which case, the inner cone would befixed to the airbag since the stationary cone is preferably fixed to theairbag. Also, as shown, the airbag interior is on the side of the outercone 878 and the airbag exterior is on the side of the inner cone 878 sothat gas is discharged from the airbag first through the openings in theouter cone and then through the openings in the inner cone. The reversesituation could also be used. Thus, in general, the set of openings ofone cone is in flow communication with the interior of the airbag andthe set of openings in the other cone is in flow communication with theexterior of the airbag so that the degree of registration or alignmentbetween the openings determines the discharge rate of gas from theairbag.

FIG. 112 is an illustration of a discharge valve including stacked driveelements. A spring 883 biases the cone 884 to the open dischargingposition. A stack of bimorph piezoelectric washers 882 when activatedclose the valve shutting off the flow out of the airbag.

The discharge valves described above can be used individually or incombination in a single airbag. To the extent possible, the dischargevalves can also be connected and controlled by a control system whichtailors the outflow rate through the discharge valve to the propertiesof the occupant. That is, an occupant sensor is provided in the vehicleto measure or determine one or more properties of an occupant and thenthe control system considers the measured or determined properties whendetermining the desired, optimum gas outflow rate and controls thedischarge valve accordingly. The control system may also consider theproperties of the crash as determined by one or more crash sensors andassociated circuitry. Such properties include the velocity change of thecrash, the acceleration of the crash and the direction of impact.

The examples shown generally illustrate the placement of the valve inassociation with the fabric of the airbag, i.e., at a location on oragainst the fabric of the airbag over a discharge opening different fromthe inlet opening of the airbag which is coupled to the inflatorstructure or inflation mechanism of the airbag. Alternately, the valvecan be placed on other structure that is in fluid communication with theinterior of the airbag. Such structure can be part of, for example, theinflator structure or inflator of the airbag.

With respect to the drive elements which move one member having openingsrelative to another, e.g., a plate, cylinder and cone, stacked driveelements could be used. That is, a stack of piezoelectric, ferroelectricor phase change alloy elements may be used to provide a short strokewith a high modulation force and millisecond response time. Also, toincrease response time into the millisecond range, a high force pre-loadwith a mechanical spring and an escarpment mechanism for triggering thedischarge valve could be used. A popit-type valve that uses theavailable air pressure to obtain gain over a single stage valve may bealso be used in accordance with the invention

Any of the valves described in International Patent Publication No.PCT/RU02/00225 could also be used in accordance with the invention inits various forms. This publication describes a safety device installedinside a vehicle having an inflatable airbag having an inlet forreceiving gas filling the airbag to its ready state, and a system forsupplying gas to the airbag, including a gas source, a valve device, anda triggering unit. The valve device is formed by a pneumatic distributorhaving two stable positions: an open position wherein gas from the gassource is fed to the airbag through its inlet, and a closed positionwherein the gas flow through the airbag inlet is interrupted.

Although multiple embodiments of discharge valves are described above,features of each can be used in the other embodiments. Also, a vehiclecan be manufactured with different discharge valves for differentairbags. Airbags including any of the discharge valves described above,or any combinations of the discharge valves described above, are alsowithin the purview of the invention.

The discharge valve of an airbag in accordance with the invention can becontrolled based on any number of criteria, including but not limited tothe morphology of the occupant to be protected by the airbag (e.g.,weight, height, etc.), the position of the occupant (either the currentposition or an extrapolated future position at which the occupant willbe at the time of airbag deployment), the severity of the crashrequiring airbag deployment, the type of occupant (i.e., adult, occupiedor unoccupied child seat, rear-facing child seat, front-facing childseat, child, pet, etc.), the direction of the crash, the position of theseat or any part thereof, and the identification of the occupying itemsin the vehicle. These criteria may be used individually or incombination to determine the appropriate control of the gas dischargerate of the airbag.

The gas discharge rate of the airbag is controlled by controlling themotor or other actuating device. To this end, the operation of the motoris studied to determine the degree of alignment of the openings in themovable member and the fixed member and thus the gas flow through theopenings, if any, for different positions of the movable plate. Then, inoperation, the motor is controlled to move the plate in the requiredmanner to provide for the desired gas discharge rate.

3.9 Airbags with a Barrier Coating

Note most of the following section was taken from U.S. Pat. Nos.6,087,016 and 6,232,389 which describe barrier coatings in general butnot for application to airbags. Quotation marks have been omitted foreasier reading.

1. Barrier Coating Mixtures

A barrier coating mixture according to this invention includes thefollowing components in a carrier liquid (i.e., aqueous or solvent):

(a) an elastomeric polymer;

(b) a dispersed, exfoliated layered platelet filler having an aspectratio greater than 25; and

(c) at least one optional surfactant, wherein the solids content isdesirably below 30% solids and the ratio of polymer (a) to filler (b) isbetween about 20:1 and 1:1. These barrier coating mixtures result infilms with reductions in permeability of 5 times to 2300 times relativeto the unfilled polymer. These results are substantially higher than theprior art on other platelet filled barrier coatings.

The barrier coating mixtures used in the invention are selected bybalancing several critical features, i.e., appropriate dispersion of thefiller in the elastomeric polymer, orientation of the filler plateletsin the elastomeric polymer, as well as high aspect ratio of the filler,in order to achieve the desired permeability reductions and flexibilityin the dried barrier coating and in the airbags. These characteristicsare demonstrated by the data shown in FIG. 113. The barrier coatingmixture of this invention desirably contains an unusually low solidscontent, i.e., between about 1% and about 30% solids. A more desirablerange of solids content is between about 5% to about 17% solids.

The solids content is an important consideration in the barrier coatingscompositions and performance of the dried coatings because the solidscontent effects the dispersion of the high aspect ratio filler. If hightotal solids content is used in the barrier coating composition, onewould not achieve well-dispersed filler, e.g., vermiculite, and thepermeability reductions characteristic of the coatings of thisinvention, and reported in the examples and figures herein, are notachieved. The preferred range of solid content (5%-17%) is unexpectedlywell below that typically used in the coating industry and therefore notpredicted by the prior art teachings concerning barrier coatingsformulations. This is especially true of the airbag industry where nosuch fillers are used prior to the teachings of this invention.

The relationship between the percentage of solids in the coatingcomposition to the weight percent of filler in the resulting driedcoating is an unexpectedly important issue in obtaining desired barriercoatings of this invention. For example, in embodiments in which thebarrier coating composition contains as the elastomeric polymer, butylrubber (Lord Corporation), and as the filler, MICROLITE® 963++vermiculite solution (W.R. Grace & Co.), FIG. 116 illustrates a range ofmaximum total solids that can be used in the coatings formulation ofthis invention without resulting in agglomeration and other negativeeffects on the dried coating (i.e., film) properties as a function ofthe fraction of the total solids made up by the filler.

In one embodiment, where the MICROLITE® filler is at 5%, the maximumsolids is about 16%; in another wherein the filler is 25%, the maximumsolids is about 9%. In still another embodiment, where the filler isabout 50%, the maximum solids is about 5%. Other examples fall withinthose ranges, as indicated in FIG. 116. The results shown in FIG. 116are based on the formulations used in Examples 9-12 discussed below.

The unusually low solids contents described in FIG. 116 for abutyl-containing polymer latex are also applicable to other elastomericpolymer latexes, as well as to elastomeric polymers in carrier liquidswhich also contain other solvents or co-solvents. One of skill in theart will understand the need to make some alterations in the maximumsprovided by FIG. 116 for other formulations of barrier coatings of thisinvention taking into account changes in electrolyte concentration,surfactants, grade and composition of vermiculite or other filler, andgrade and composition of polymeric latex or other elastomeric polymer ina carrier as described herein.

If desired, the solids content of the barrier coating mixtures can befurther adjusted to levels below the maximums shown in FIG. 116 usingthickeners, in order to adjust the final film thickness, as well as toadjust the suspension rheology. See, for example, Examples 14-15 whichdemonstrate the increase in viscosity from 4.5 cP to 370 cP using PVOHterpolymer; and Example 16 which similarly increases viscosity usinglithium chloride as a thickener. Other conventionally used thickenersmay also be useful.

The solids content of the coating mixtures of this invention ispreferably based upon a preferred polymer to filler ratio of betweenabout 20:1 to about 1:1, more preferably 9:1 to 1:1, particularly whenthe polymer is a butyl-containing polymer such as a butyl latex, and thefiller is a vermiculite solution. Examples 9-12 indicate a variety ofdesirable compositions of this invention characterized by a polymer tofiller ratios within the above range, over a range of solids contents,polymer contents by weight and filler contents by weight.

Preferably, in the dried barrier coating (film), the polymer is presentat between about 45 to about 95 by weight and the dispersed layeredfiller is present at between about 5 to about 55% by weight.

A. The Elastomeric Polymer

Elastomeric polymers useful in forming coating mixtures of thisinvention include polymers selected generally from among many classes.The selected polymers may be curable polymers, partially cured polymers,or uncured polymers, and may be soluble in water or a solvent. Suchpolymers include, without limitation, olefinic thermoplastic elastomer(TPO); polyamide thermoplastic elastomer (Polyamide TPE); polybutadienethermoplastic elastomer, e.g., syndiotactic 1,2-polybutadienethermoplastic elastomer (polybutadiene TPE); polyester thermoplasticelastomer (Polyester TPE); polyurethane thermoplastic elastomer (TUPR),for example, thermoplastic polyester-polyurethane elastomer (TPAU), andthermoplastic polyether-polyurethane elastomer (TPEU); styrenicthermoplastic elastomer (Styrenic TPE); vinyl thermoplastic elastomer,e.g., polyvinyl chloride polyol (pPVC).

A variety of rubbery polymers (curable, partially cured, or uncured) mayalso be employed as the polymer component of the present invention,including acrylic rubber, such as ethylene-acrylate copolymer (EACM);and butadiene rubber, such as polybutadiene. Butyl-containing polymersuseful in forming coating mixtures of this invention include, withoutlimitation, curable, partially cured, or uncured polymers: butyl rubber,such as isobutylene-isoprene copolymer (IIR); bromobutyl rubber, e.g.,bromoisobutylene-isoprene copolymer (BIIR); chlorobutyl rubber, e.g.,chloroisobutylene-isoprene copolymer (CIIR); and isobutylene rubber.Butyl rubber is defined as a poly(isobutylene) homopolymer or acopolymer of poly(isobutylene) with isoprene. Modified butyl rubbersinclude halogenated poly(isobutylene) and its copolymers and isoprene.Additional polymers or copolymers that contain more than 50% isobutyleneare also useful in the practice of this invention, for example,poly(isobutylene-co-acrylonitrile), etc. Other butyl-containing polymerswhich are curable, partially cured or uncured, may be readily selectedby one of skill in the art.

Still other useful elastomeric polymers are chlorosulfonatedpolyethylene rubber, e.g., chlorosulfonated polyethylene (CSM);epichlorohydrin rubber, such as polyepichlorohydrin (CO),polyepichlorohydrin copolymer (CO copolymer); ethylene-propylene rubber(EPR), such as ethylene-propylene copolymer (EPM),ethylene-propylene-diene copolymer (EPDM).

Other polymers for such use include fluoroelastomers, such as vinylidenefluoride-hexafluoropropylene copolymer (FKM); natural rubber (NR);neoprene rubber such as polychloroprene (CR); nitrile rubber, such asacrylonitrile-butadiene copolymer (NBR); polyisoprene rubber (PI);polysulfide rubber; polyurethane, such as polyester urethane (AU), andpolyether urethane (EU); propylene oxide rubber; silicone rubber, suchas silicone (MQ), and methylvinyl-fluorosilicone (FVMQ) andstyrene-butadiene rubber, such as styrene-butadiene copolymer (SBR).

The polymer is preferably capable of forming a solution, dispersion,latex, suspension or emulsion in water or a solvent, or a mixturethereof. Specifically exemplified below is a coating mixture of theinvention employing as the elastomeric polymer, butyl latex. A suitablecommercially available butyl latex for use in the compositions of thisinvention is Lord® BL-100 butyl latex, which is a 62% by weight aqueousbutyl latex solution [Lord Corporation]. Another suitable butyl latex,the use of which is illustrated in Example 10, is Polymer Latex ELRbutyl latex, a 50% butyl latex solution (Polymer Latex). Still anothersuitable polymer is a 51.7% bromo-butyl latex solution available fromPolymer Latex (see Examples 11-12). These latexes contain an ionicsurfactant package which stabilizes the latex and effects theperformance of the barrier formulation. Other butyl latexes areanticipated to be similarly useful if combined with similar ionicsurfactants. Preferably, the selected polymer is present in the driedcoating mixture at a minimum of about 45% by weight of the driedcompositions.

B. The Filler

The coating mixtures of this invention as described above also include adispersed layered filler which, upon mixture, has an inherently highaspect ratio, which can range from about 25 to as high as about 30,000.The presently preferred filler is vermiculite. More particularly, adesirable vermiculite is. MICROLITE® 963++water-based vermiculitedispersion (W. R. Grace) [see, EP Application No. 601,877, publishedJun. 15, 1994] which is a 7.5% by weight aqueous solution of dispersedmica. One novel aspect of the mixtures of the present invention is theeffective aspect ratio of the selected filler in the dried coating.According to this invention, in the dried coating, the filler remainssubstantially dispersed, thereby having a “high effective aspect ratio”,as shown in FIG. 113. FIG. 113 assumes high levels of orientation.

Preferably, the effective aspect ratio of the filler in the compositionsof this invention is greater than 25 and preferably greater than about100, although higher ratios may also be obtained. In embodiments inwhich orientation is not high, the effective aspect ratio required forlarge reductions in permeability will be higher than 100. In the coatingmixtures (the liquid), the layered filler is present at between about 1to about 10% by weight of the total mixture. In the dried coatings ofthis invention, the layered filler is present at a minimum of about 5%by weight to a maximum of about 55% of the dried coating. Thecompositions of the present invention, when dried, retain the filler inwell-dispersed form, resulting in a high effective aspect ratio of thedried coating, and greatly increased reduction in permeability, asillustrated in FIG. 113.

MICROLITE® vermiculite is the preferred filler because of its very highaspect ratio. The vermiculite plates have an average lateral size ofbetween 10 and 30 microns. The plates are largely exfoliated in water,and thus their thickness is 1-2 nm. The aspect ratio of the filler inwater dispersion is an average of 10,000-30,000. It is clear that manyplates reassemble during the coating and drying process of the presentinvention, thus reducing the effective aspect ratio achieved in thefinal coating. However, it is a great advantage to start with as largean aspect ratio as possible.

Although MICROLITE® 963++ vermiculite (W. R. Grace) is preferred, goodresults may also be achieved with less exfoliated grades of MICROLITE®vermiculite (i.e., grades 963, 923, and 903referenc). Other layeredsilicates are also useful in the barrier coatings and films of thisinvention. The effectiveness of other silicates in the barrier coatingof this invention depends upon the lateral size of the platelets, thedegree of exfoliation in water, and the degree to which they reassembleto form larger particles during the coating and drying process. Examplesof other layered silicates include bentonite, vermiculite,montmorillonite, nontronite, beidellite, volkonskoite, hectorite,saponite, laponite, sauconite, magadiite, kenyaite, ledikite andmixtures of the above silicates. The selection and use of other knownsilicates which have properties similar to those of MICROLITE®vermiculite, as well as sufficiently high aspect ratios, are expected tobe obvious to one of skill in the art following the teachings of thisinvention.

C. Surfactants and Other Additives

Coating mixtures used in the invention, particularly those useful onsurfaces and interfaces according to this invention, also preferablycontain at least one or more suitable surfactant to reduce surfacetension. Surfactants include materials otherwise known as wettingagents, anti-foaming agents, emulsifiers, dispersing agents, levelingagents etc. Surfactants can be anionic, cationic and nonionic, and manysurfactants of each type are available commercially. A suitablesurfactant for inclusion in these compositions possesses a criticalmicelle concentration sufficiently low to ensure a dried coatinguncompromised by residual surfactant.

Preferably, the surfactant(s) useful in the methods and solutions ofthis invention are nonionic, particularly useful with a highly chargedfiller, such as vermiculite. In the event of an unfavorable interactionof the anionic emulsifier present in the butyl latex dispersion [Lord],which is a presently preferred source of the butyl-containing polymer,any additional ionic additives must be kept to a minimum. This variableis eliminated where the surfactant or emulsifier is non-ionic. Increasein ionic concentration of the compositions containing vermiculite, suchas by the addition of a base to adjust pH, e.g., LiOH, NH₄OH, and NaOHcan cause agglomeration of the filler, which adversely affectspermeability reduction.

Some embodiments of this invention include at least two surfactants,which include preferably both a wetting agent and an anti-foaming agent.Still other compositions may have additional surfactants to performadditional effects. Desirable surfactants employed in the examples beloware the non-ionic siloxane-based, Silwet® L-77 wetting agent [OSISpecialties, Inc.], the BYK®-306 wetting/leveling agent [BYK Chemie],FOAMASTER® VL defoamer (Henkel), and the DC200® anti-foaming agent [DowCorning], among others. As exemplified below, an antifoaming agent maybe predispersed in solution with, e.g., 1-methyl-2-pyrrolidinone (NMP)because some antifoaming agents are not soluble in the barrier coating.

Other suitable surfactants may also be selected. The amount and numberof surfactants added to the coating solution or composition will dependon the particular surfactant(s) selected, but should be limited to theminimum amount of surfactant that is necessary to achieve wetting of thesubstrate while not compromising the performance of the dried coating.For example, typical surfactant amounts can be less than or equal toabout 10% by weight of the dried coating.

In another embodiment, thickeners may be used in the coatingformulations to adjust viscosity. Such thickeners may include, withoutlimitation, a polyvinyl alcohol (PVOH) terpolymer, e.g.,polyvinylbutyral/polyvinylacetate/polyvinylalcohol or a lithium chloridethickener. In one embodiment, the viscosity of the coating mixture canbe increased from 4.5 cP to 370 cP with the addition of the PVOHterpolymer to the formulation as illustrated in Examples 14-15. Forexample, for a coating mixture containing 10% total solids with 2%MICROLITE® vermiculite formulation, a thickener such as PVOH terpolymercan be added in an amount of between about 3% to about 5.5% by weight.Desirably the thickener is added in an amount of greater than 3.5% byweight. A preferred range of thickener is between about 5 and 5.5% byweight.

It has been noted that greater than 5.5% by weight of PVOH terpolymerthickener can cause agglomeration of the filler platelets. As anotherexample, the viscosity of the coating mixture can also be increased withthe addition of lithium chloride as a thickener to the coating mixture,(See e.g., Example 16). For example, for a coating mixture containing10% total solids with 2% MICROLITE®, the thickener is employed in anamount between about 3% to about 5% by weight. Desirably greater than 4%thickener is employed, and more desirably 5% thickener is employed.Greater than 5% by weight of the lithium chloride thickener producespoor barrier properties. One of skill in the art would readily determineand adjust the type and amounts of thickener depending on the type andamount of filler employed in the coating mixture based on the teachingscontained herein.

Still other optional components of the barrier coating are componentswhich effect curing of the coating. For example, one type of cure“package” contains about 10 to about 30% by weight zinc oxide, about 5to about 20% by weight sulfur, about 30 to about 60% by weight water,about 0.1 to about 10% of a dispersing agent, about 5 to about 20% ofzinc dibutyldithio-carbamate and about 1 to about 10% zinc2-mercaptobenzothiazole. The amount of cure package added to the coatingmixture is based on the amount of butyl rubber in the coating mixture.

In one embodiment, greater than 10 parts dried cure package is added per100 parts butyl rubber in the coating mixture. A desirable amount ofdried cure package is about 15 parts cure package per 100 parts butylrubber in the mixture. One of skill in the art can readily design a cure“package” to enhance the curing of a butyl latex barrier coating mixtureof this invention, and select a desirable amount to be added to thecoating mixture, based on the teachings of this specification combinedwith the knowledge of the art. See, e.g., U.S. Pat. No. 4,344,859.

D. The Carrier Liquid

The coating mixtures of this invention are present in a suitable carrierliquid. Carriers which are suitable for use in the composition of thisinvention include, without limitation, water and solvents such ashexane, heptane, toluene, 1 methyl-2-pyrrolidinone, cyclohexanone,ethanol, methanol, and other hydrocarbons. Combinations of water with anorganic carrier may also be used as the carrier liquid. Selection of asuitable organic solvent carrier is within the skill of the art.

E. Specific Embodiments of Barrier Mixtures

One example of a barrier coating mixture useful for application tosubstrates such as a fabric portion of an airbag and in particular aside curtain airbag according to this invention comprises coating formedby a barrier coating mixture comprising in a carrier liquid: (a) anelastomeric polymer; (b) a dispersed exfoliated layered platelet fillerpreferably having an aspect ratio greater than 25; and optionally (c) atleast one surfactant. The elements are selected so that the solidscontent of the mixture is less than about 30% and the ratio of thepolymer to the filler is preferably between about 20:1 and about 1:1.These barrier coating mixtures result in films with reductions inpermeability of 5 times to 2300 times relative to the unfilled polymer.These results are substantially higher than the prior art on otherplatelet filled barrier coatings or any airbag coatings.

Another barrier coating mixture which is desirable for application to afabric portion of an airbag according to this invention includes thefollowing components in a carrier liquid, (a) a butyl-containing polymerlatex; (b) a dispersed exfoliated layered vermiculite filler preferablyhaving an aspect ratio about 1000 or greater; and optionally (c) atleast one surfactant. The components are selected such that the solidscontent of the mixture is less than abut 17% and the ratio of thepolymer to the filler is between about 20:1 and about 1:1.

In a preferred embodiment, the coating mixtures described above havesolids contents of between about 5% to about 15% by weight, and formdried coatings on the airbag surface that comprise between about 45% toabout 95% by weight of the polymer, between about 5% to about 55% byweight of the filler, and between about 1.0% to about 10% by weight ofthe surfactant(s). The dried coatings of the mixtures described above,contain fillers which preferably exhibit an effective aspect ratio ofgreater than about 25, reduces the gas, vapor or chemical permeabilitygreater than 5-fold that of the dried, unfilled polymer alone.Preferably, the effective aspect ratio of the dried coatings is greaterthan about 50, and even greater than about 100.

One preferred coating mixture useful in this invention has a solidscontents of between about 5% to about 15% by weight and the driedcoating comprises between about 65% to about 90% by weight of abutyl-containing polymer latex, between about 10% to about 35% by weightof a vermiculite filler, between about 0.1% to about 0.10% by weight ananti-foaming agent as surfactant, with the total surfactant weightpercent up to about 15%. As described in examples below, the selectedpolymer is the elastomer butyl rubber or butyl latex, e.g., Lords BL-100butyl latex in a 62% by weight aqueous butyl latex solution [LordCorporation]. Additional preferred barrier coating mixtures useful inthis invention may be prepared by methods described in detail inExamples 1-12 and 14-16.

2. The Coated Article

Once prepared as described in detail in the Examples below, the coatingmixtures may be applied to a portion of fabric which will beincorporated into or sewn to form an airbag of a vehicle, to reduce thepermeability of the fabric to gas, vapor (moisture) or chemicals. Thedried coating, in which the filler exhibits an effective aspect ratio ofgreater than about 25, reduces the gas, vapor or chemical permeabilitygreater than 5-fold that of the dried, unfilled polymer alone. In thedried coating, more preferably, the polymer is present in the mixturewhen dried at a weight percent of at least about 45%. The filler ispreferably present in the mixture when dried at greater than about 5% byweight. These barrier films achieve reductions in permeability of 5times to 2300 times relative to the unfilled polymer. These results aresubstantially higher than the prior art on other platelet filledelastomers.

Preferably, the effective aspect ratio of the dried coating is greaterthan about 50, and even greater than about 100. As indicated in Examples1-12, reductions in permeability attributed to compositions of thisinvention can range from approximately 5 times to 2300 times that ofunfilled polymer alone.

The coating compositions used in the invention may be applied on theinside of the fabric, i.e., on a portion of the fabric which, once theairbag is formed, will face the interior gas-receiving compartment ofthe airbag. The coating is applied by standard techniques, with spraycoating and dip coating likely to be the most effective.

The present invention substantially reduces the weight of a side curtainairbag, for example, by providing equivalent sealing of the fabricthereby reducing the flow of the inflation gas through the materialusing substantially less sealing material. Typically, the weight of thesealant is reduced by a factor of five or more. However, much of theleakage occurs through the seams and sealing the fabric will not reducethis leakage. Most side curtain airbags are currently sealed at theedges by sewing or interweaving where the entire airbag is woven atonce. In the first case, the sewing threads make holes in the fabric andserve as a path for gas leakage. In the second case, interweavingresults in a leakage path since when the airbag is pressurized thestresses in the seams separate the threads at the joints again creatingleakage paths. A preferred method is to heat or adhesive seal the piecesof fabric together and to do so over an extended seam width therebyeliminating the leakage paths. Since such seals are often weaker than asewn or woven seam, careful attention must be given to the design of theairbag chambers to prevent stress concentrations in the seams. Thisfrequently requires a finite analysis and redesign of the individualchambers in order to eliminate such stress concentrations.

The airbag may be formed completely by interweaving, heat sealing orsewing of the layers before the barrier coating is applied. Currently,airbags are often formed this way but without a barrier coating. Ingeneral, any known technique for manufacturing an airbag can be appliedto make an airbag in accordance with the invention, i.e., an airbag madeof one or more substrates and a barrier coating.

A selected barrier coating mixture, such as those described above may beapplied to a surface or interface of a fabric section to be incorporatedinto an airbag to accomplish a variety of purposes in the airbagmanufacturing industries to reduce the permeability of the airbag togas, vapor or chemicals.

3. Methods of Coating a Substrate or Forming a Film

The fabric sections to be coated by the compositions of the inventionmay be previously untreated or may have a variety of pre-treatments totheir surfaces. For example, the fabric sections may have on at leastone side a heat seal layer. Such heat seal layers may be made of anethylene-propylene copolymer or ethylene-propylene-butylene terpolymer.Thus, the coating solution is applied on the surface of the heat seallayer. Alternatively, the fabric sections may comprise a protectivetopcoat layer, such as polyurethane or Teflon®-type materials [DuPont]for abrasion resistance, etc. Such topcoats may be selected by one ofskill in the art. The coatings of this invention may be applied over orunder the topcoat layer.

Alternatively, the article may be cured prior to application of thecoating, or it may be cured following application of the coating on theappropriate surface.

To form the coated article of this invention, the application of theselected barrier coating mixture may be accomplished by techniquesincluding, without limitation, roller transfer or paint coating, spraycoating, brush coating and dip coating. Roll coating techniques include,but are not limited to, rod, reverse roll, forward roll, air knife,knife over roll, blade, gravure and slot die coating methods. Generaldescriptions of these types of coating methods may be found in texts,such as Modern Coating and Drying Techniques, (E. Cohen and E. Gutoff,eds; VCH Publishers) New York (1992) and Web Processing and ConvertingTechnology and Equipment, (D. Satas, ed; Van Nostrand Reinhold) New York(1984). Three dimensional articles may preferably be coated by thetechniques which include, but are not limited to, spray coating or dipcoating. The method of application is not a limitation on the presentinvention, but may be selected from among these and other well-knownmethods by the person of skill in the art. However, the coating must beapplied so that drying takes place on the substrate and not in the air(i.e. powder coating). If drying takes place during spraying or othermeans of application, agglomeration may occur.

The coating mixtures may be applied to a fabric substrate, such as anexterior or interior surface, an interface, or component of the airbag,at any desired thickness. Thus, for example, the coating mixtures of thepresent invention may be applied to the surface of fabric sections bythe methods described above to form a dried coating of a thicknessbetween about 0.1 (m to about 100 (m of dry coating. Such adjustments tothickness are well within the skill of the art [see, e.g., CanadianPatent No. 993,738].

After coating, the coated airbag, may be dried at a selectedtemperature, e.g., room temperature or greater than room temperature.The selection of the drying temperature, relative humidity, andconvective air flow rates depends on the desired time for drying; thatis, reduced drying times may be achieved at elevated air temperatures,lower relative humidity and higher rates of air circulation over thedrying coating surface. After drying, the exfoliated silicate fillerparticles are oriented within the elastomeric latex (solution, emulsion,etc.) to a high degree parallel to each other and to the airbagsubstrate surface. One of skill in the art can readily adjust the dryingconditions as desired. The performance of the dried barrier coating isinsensitive to drying temperatures over the range 25-160° C.

The dried coatings exhibit a surprising reduction in permeabilitycompared to the prior art and particularly compared to unfilledpolymers.

The dried coating preferably maintains its low permeability afterrepeated mechanical loading and elongation up to about 10% of theairbag. The evaluation of the coating integrity after exposure torepeated loading and elongation was examined as described below inExample 17.

The coatings and methods of the present invention described above may beapplied to the manufacture or repair of airbags to improve air or gasretention. The barrier coatings may allow reduced mass, reduced gaspermeability resulting in better air retention, reduced thermo-oxidativedegradation, and enhanced wear and elongation of the useful life of thearticle.

Referring now to FIGS. 120, 121, 122A and 122B, an airbag module inaccordance with the invention is designated generally as 890 andcomprises a module housing 891 in which an airbag 892 is folded. Thehousing 891 may be arranged in any vehicle structure and includes adeployment door 893 to enable the airbag to deploy to protect theoccupants of the vehicle from injury. Thus, as shown, the housing 891may be mounted in the ceiling 894 of the vehicle passenger compartment895 to deploy downward in the direction of arrow A as a side curtainairbag to protect the occupants during the crash.

As shown in FIG. 122A, one embodiment of the airbag 892 comprises asubstrate 896 and a barrier coating 897 formed on the substrate 896,either on the inner surface which will come into contact with theinflation fluid or on an outer surface so that the barrier coating 897will come into contact only with inflation fluid passing through thesubstrate 895. The airbag 892 may be formed with any of the barriercoatings described herein. In one embodiment, a flat sheet of thesubstrate 896 would be coated with the barrier coating 897 and then cutto form airbags having an edge defining an entry opening for enablingthe inflation of the airbag. The edge 898 of the airbag 892 would thenbe connected, e.g., by sealing, to a part 899 of the housing 891 whichdefines a passage through which the inflation fluid can flow into theinterior of the airbag 892 (see FIG. 121). The inflation fluid may begenerated by an inflator 900 possibly arranged in the module housing891.

In the embodiment shown in FIG. 122B, the barrier coating 897 is placedbetween two substrates 896, 901. Any number of substrates and barriercoatings can be used in the invention. Also, the number of substratesand barrier coatings can be varied within a single airbag to provideadditional substrates and/or barrier coatings for high stresses areas.

Referring now to FIG. 123, a method for designing a side curtain airbagin accordance with the invention will now be described. It is a problemwith side curtain airbags that since they are usually formed of twopieces of material, the manner of connecting the pieces of materialresults in leakage at the seams.

To avoid this problem, in the invention, two pieces of material, forexample, a piece of fabric with a barrier coating as described herein,are cut (step 902) and edges of the two pieces are sealed together toform an airbag while leaving open an entry opening for inflation fluid(step 903). The location of partition lines for partitioning the airbaginto a plurality of compartments, e.g., a plurality of parallelcompartment each of which is receivable of inflation fluid and adaptedto extend when inflated vertically along the side of the vehicle, isdetermined (step 904) and it is determined whether the stresses are atthe seams (step 905). If not, the design is acceptable (step 906).Otherwise, the airbag is re-designed until stresses are not created atthe seams during inflation or a minimum of stress is created at theseams during inflation. The determination of the location of thepartition lines may involve analysis of the airbag using finite elementtheory.

This embodiment of the invention is illustrated by non-limiting examples(Examples 1-17) set forth in U.S. patent application Ser. No.10/413,318, which is incorporated by reference herein.

4 Systems

4.1 Self-Contained Airbag Systems

Self-contained airbag systems contain all of the parts of the airbagsystem within a single package, in the case of mechanicalimplementations, and in the case of electrical or electronic systems,all parts except the primary source of electrical power and, in somecases, the diagnostic system. This includes the sensor, inflator andairbag. Potentially, these systems have significant cost and reliabilityadvantages over conventional systems where the sensor(s), diagnostic andbackup power supply are mounted separate from the airbag module. Inmechanical implementations in particular, all of the wiring, thediagnostic system and backup power supply are eliminated.

FIG. 22 is a perspective view of a side impact airbag systemillustrating the placement of the airbag vents in the door panel andexhausting of the inflator gases into the vehicle door and also showingthe use of a pusher plate 190 to adjust for the mismatch between thepoint of impact of an intruding vehicle and the sensor of aself-contained side impact airbag system. The pusher plate 190 is shownattached to the main structural door beam 191 in this illustration butother mounting systems are also possible. The pusher plate 190 isdimensioned and installed in the door so that during a side impact toany portion of the side of the vehicle which is likely to causeintrusion into the passenger compartment and contact an occupant, thepusher plate will remain in a substantially undistorted form until ithas impacted with the sensor causing the sensor to begin deployment ofthe airbag. In this implementation, a non-sodium azide propellant, suchas nitro-cellulose, is used and the gas is exhausted into the doorthough a pair of orifices 192 (only one of which is shown). The airbagsystem may be any of those disclosed herein.

FIG. 23 is a cross-sectional view of a self-contained side impact airbagsystem using an electronic sensor that generates a signal representativeof the movement of a sensing mass. Unless otherwise stated orinconsistent with the following description of an airbag system with anelectronic sensor, the airbag system with an electronic sensor mayinclude the features of the airbag system described above and below. Anelectronic sensor is one in which the motion of the sensing mass istypically continuously monitored with the signal electronicallyamplified with the output fed into an electronic circuit which isusually a micro-processor. Electronic sensors typically useaccelerometers that usually make use of micromachined, SAW, strain gageor piezo-electric elements shown here as 193. The accelerometer element193 generates a signal representative of the movement of the sensingmass.

Modern accelerometers are sometimes micro-machined silicon and combinedwith other elements on an electronic chip. In electro-mechanicalsensors, the motion of the sensing mass is typically measured inmillimeters and is much larger than the motion of the sensing mass inelectronic sensors where the motion is frequently measured in microns orportions of a micron. The signal representative of the motion of thesensing mass is recorded over time and an algorithm in themicroprocessor may be designed to determine whether the movement overtime of the sensing mass results in a calculated value that is in excessof the threshold value based on the signal. The sensing mass mayconstitute part of the accelerometer, e.g., the sensing mass is amicro-machined acceleration sensing mass. In this case, themicroprocessor determines whether the movement of the sensing mass overtime results in an algorithmic determined value that is in excess of thethreshold value based on the signal.

For side impact electronic sensors, the acceleration of the sensing massis acceleration in a lateral direction or lateral acceleration since thepassenger compartment is inward relative to the side of the vehicle.

In embodiments using an electronic sensor, the inflator may include aprimer that is part of an electronic circuit including the accelerometersuch that upon movement over time of the sensing mass which results in acalculated value in excess of the threshold value, the electroniccircuit is completed thereby causing ignition of the primer. In thiscase, the primer may be initiated electronically through a bridge orsimilar device that is initiated electronically.

When the term electrical is used herein, it is meant to include bothelectro-mechanical and electronic systems. FIG. 24 is a schematic of anexemplifying embodiment of an electric circuit of an electro-mechanicalor electronic side impact airbag system in accordance with theinvention. The self-contained module implementation shown generally at194 contains a sensor assembly 204 and an airbag and inflator assembly202. The sensor assembly 204 contains a sensor 205, a diagnostic module206, an energy storage capacitor 207, and a pair of diodes 203 toprevent accidental discharge of the capacitor 207 if a wire becomesshorted. The module 206 is electrically connected to a diagnosticmonitoring circuit 208 by a wire 195 and to the vehicle battery 209 by awire 197. The module 206 is also connected to the vehicle ground. Thesensor, diagnostic and capacitor power supplies are connected to thesquib by wires 199-201.

In a basic configuration, the diagnostic monitoring circuit 208 checksthat there is sufficient voltage on the capacitor 207 to initiate theinflator assembly 202 in the event of an accident, for example, andeither of wires 195, 197 or 198 are severed. In this case, a diagnosticcomponent internal to the self-contained module would not be necessary.In more sophisticated cases, the diagnostic module 206 could check thatthe squib resistance is within tolerance, that the sensor calibration iscorrect (through self testing) and that the arming sensor has notinadvertently closed. It could also be used to record that the armingsensor, discriminating sensor and airbag deployment all occurred in theproper sequence and record this and other information for futureinvestigative purposes. In the event of a malfunction, the diagnosticunit could send a signal to the monitoring circuitry that may be no morethan an indication that the capacitor 207 was not at full charge. Otherrelated circuit components include capacitor 211 and resistor 210.

A substantial improvement in the reliability of the system is achievedby placing the diagnostic module and backup power supply within theself-contained airbag system particularly in the case of side impactswhere the impact can take place at any location over a wide area. Animpact into a narrow pole at the hinge pillar, for example, might besufficient to sever the wire from the airbag module to the vehicle powersource before the sensor has detected the accident. The placement of anelectronic self-contained airbag module in the steering wheel alsoprovides for significant economic and reliability improvementsespecially since the energy needed to trigger the airbag can be storedon the capacitor and does not need to be transmitted to the modulethrough the “clock spring” coiled ribbon cable that connects thesteering wheel horn, switches etc. to vehicle power. Thus, thecurrent-carrying capability of the clock spring can be substantiallyreduced.

Most of the advantages of placing the sensor, diagnostic and backuppower supply within the self-contained module can of course be obtainedif one or more of these components are placed in a second module inclose proximity to the self-contained module. For the purposes ofelectro-mechanical or electronic self-contained modules, therefore, asused herein, the terms “self-contained module” or “self-contained airbagsystem” will include those cases where one or more of the componentsincluding the sensor, diagnostic and backup power supply are separatefrom the airbag module but in close proximity to it. For example, in thecase of steering wheel-mounted systems, the sensor and backup powersupply would be mounted on the steering wheel and in the case of sideimpact door mounted systems, they would be mounted within the door orseat. In conventional electrical or electronic systems, on the otherhand, the sensor, diagnostic module and backup power supply are mountedremote from the airbag module in a convenient location typicallycentrally in the passenger compartment such as on the tunnel, under theseat or in the instrument panel.

With the placement of the backup power supply in the self-containedmodule, greater wiring freedom is permitted. For example, in some casesfor steering wheel-mounted systems, the power can be obtained throughthe standard horn slip ring system eliminating the requirement of theribbon coil now used on all conventional driver airbag systems. For sideimpact installations, the power to charge the backup power supply couldcome from any convenient source such as the power window or door lockcircuits. The very low resistance and thus high quality circuits andconnectors now used in airbag systems are not required since even anintermittent or high resistance power source would be sufficient tocharge the capacitor and the existence of the charge is diagnosed asdescribed above.

Herein, the terms capacitor, power supply and backup power supply areused interchangeably. Also, other energy storage devices such as arechargeable battery could be used instead of a capacitor. For thepurposes of this disclosure and the appended claims, therefore, the wordcapacitor will be used to mean any device capable of storing electricalenergy for the purposes of supplying energy to initiate an inflator.Initiation of an inflator will mean any process by which the filling ofan airbag with gas is started. The inflator may be either purepyrotechnic, stored gas or hybrid or any other device which provides gasto inflate an airbag.

FIG. 25 is a side view showing the preferred mounting of twoself-contained airbag modules 212 and 213 on the side on a two doorvehicle. Module 212 is mounted inside of a door, whereby the sensorhousing of module 212 is most proximate the exterior of the vehicle,while module 213 is mounted between the inner and outer side panels at alocation other than the door, in this case, to protect a rear seatedoccupant. Each module has its own sensor and, in the case of electricalself-contained systems, its own capacitor power supply and diagnosticcircuit. Any of the airbag systems disclosed herein may be mountedeither inside a door or between inner and outer side panels of thevehicle at a location other than the door and for non-self-containedsystems, the sensor can be mounted anywhere provided there is asufficiently strong link to the vehicle side so that the sensor isaccelerated at a magnitude similar to the vehicle side crush zone duringthe first few milliseconds of the crash. In view of the mounting ofmodule 213 between inner and outer panels of the vehicle at a locationother than the door, the inner and outer panels are thus fixed to thevehicle frame and the module 213 is also thus fixed to the frame. Bycontrast, the module 212 mounted inside the door is moved whenever thedoor is opened or closed.

This invention is also concerned with a novel self-contained airbagsystem for protecting occupants in side impacts and in particular withthe sensors used either with self-contained modules or apart from theairbag module. This is accomplished by using the sensors described inU.S. Pat. No. 5,231,253, along with other improvements described indetail below. This invention is also concerned with applying some of thefeatures of the novel side impact system to solving some of the problemsof prior art mechanical airbag systems discussed above.

The inflator mechanism may be any component or combination of componentswhich is designed to inflate an airbag, preferably by directing gas intoan interior of the airbag. One embodiment of the inflator mechanism maycomprise a primer. In this case, the crash sensor includes an electroniccircuit including the accelerometer and the primer such that uponmovement over time of the sensing mass results in a calculated value inexcess of the threshold value, the electronic circuit is completedthereby causing ignition of the primer.

4.2 Occupant Sensing

In U.S. Pat. Nos. 5,829,782 and 5,563,462, the use of neural networks asa preferred pattern recognition technology is disclosed identifying arear facing child seat located on the front passenger seat of anautomobile. These patents also disclose many other applications ofpattern recognition technologies for use in conjunction with monitoringthe interior of an automobile passenger compartment and more generally,monitoring any interior space in a moving vehicle which might beoccupied by an object.

FIG. 26 illustrates an occupant monitoring system that is capable ofidentifying the occupancy of a vehicle and measuring the location andvelocity of human occupants. This system is disclosed in detail in U.S.RE37260. In this preferred implementation, four transducers 220, 221,222 and 223 are used to provide accurate identification and positionmonitoring of the passenger of the vehicle. A similar system can beimplemented on the driver side or rear seat. In FIG. 26, linesconnecting the transducers C and D and the transducers A and B aresubstantially parallel permitting an accurate determination of asymmetryand thereby object rotation as described in U.S. RE37260.

The system is capable of determining the pre-crash location of thecritical parts of the occupant, such as his/her head and chest, and thento track their motion toward the airbag with readings as fast as onceevery 10 milliseconds. This is sufficient to determine the position andvelocity of the occupant during a crash event. The implementationdescribed in U.S. RE37260 can therefore determine at what point theoccupant will get sufficiently out-of-position so that deployment of theairbag should be suppressed. In the instant invention, the same data isused but instead of only making a trigger/no-trigger decision, theinformation is also used to determine how fast to deploy the airbag, andif the weight of the occupant is also determined in a manner such asdisclosed in U.S. Pat. No. 5,748,473, the amount of gas which should beinjected into the airbag and perhaps the outflow resistance can becontrolled to optimize the airbag system not only based on the crashpulse but also the occupant properties. This provides the design forPhase 3 Smart Airbags.

In U.S. Pat. No. 5,684,701, concern was expressed about a possiblecontention for processor resources when multiple systems were using thesame microprocessor. This is no longer a problem with the availabilityof neural computer designs that can be incorporated into an ASIC forthis system. Such designs utilize a parallel computing architecture tocalculate all of the node calculations simultaneously. Furthermore, theneural computer can be made with as many input nodes as desired withlittle penalty in ASIC cost. Thus, both the calculation of the positionof the occupant and the crash pulse analysis can occur at the same time.

In the neural network ASIC design, it is anticipated that, for mostapplications, the node weights will be read in at execution time.Therefore, a single neural network hardware design can perform manypattern recognition functions as long as the functions that share theneural computer do not need to be done at the same time. To the extentthat this sharing can be done, each of these non-critical features canbe added at very little additional cost once one system is implemented.

In FIG. 26A, an alternate view of the passenger compartment of a motorvehicle is presented which illustrates an occupant out-of-positionsensor and a rear facing child seat detector, both located on theA-pillar of the vehicle and both using the same neural computer as theneural network crash sensor. In other applications, these transducersare mounted on other locations such as the B-pillar and headliner. Thus,once one neural network application for an automobile is implemented,the same neural network computer system can be used for several patternrecognition applications.

Use of the neural network to identify or detect a rear facing child seatoccurs when the vehicle is first put in motion. In contrast, use of theneural network for crash pattern recognition occurs continuously butneed only take place when an abnormal event is taking place. Since it ishighly unlikely that both events will take place simultaneously, thesame system can easily accomplish both tasks. In event of a conflict,one of the functions takes priority. A strong motivation for the use ofa neural network crash sensor, therefore, in addition to its superiorperformance, is that substantial economies result. Use of neuralnetworks for interior vehicle monitoring or for crash sensing is notbelieved to have been discovered prior to its discovery by the currentassignee, let alone the greater advantage of combining both functionswith the same neural network system. When the added requirement ofdetermining the position of an occupant dynamically is considered, thechance of a conflict between the occupant sensing and the crash sensingsystems increases since both must be done continuously. Both systems canstill use the same neural network system providing the processor is fastenough. One method of assuring that this is true is to use a parallelprocessor, such as a neural computer.

An interesting point is that each feature can be added at very littleadditional cost once one system is implemented. The distance measurementto determine an out-of-position occupant is a minor software change andthe addition of the driver system once a passenger system is in place,or vice versa, requires only additional transducers which areinexpensive in large quantities. Since both the driver and passengersystems can share the same electronics, there will be virtually noadditional cost for electronic components.

In FIG. 26A, four ultrasonic transducers 224, 225, 226, and 227, areused to identify an object occupying the front passenger seat asdescribed in U.S. Pat. Nos. 5,563,462 and 5,829,782. In this particularimplementation, an additional transducer 224 is provided to improve theidentification accuracy of the system. Ultrasonic transducers 228 and229 are used to determine the distance from the transducers to thevehicle driver and ultrasonic transducers 230, 231 and 232 are used tomeasure the distance to the steering wheel mounted airbag module 51 andalso to the driver. The second measurement of the driver's position isused to confirm the measurements obtained from transducers 228 and 229.The distance from the airbag can be calculated knowing the distance tothe driver and the distance to the steering wheel 233. Other types oftransducers or measurement devices could be used without deviating fromthe teachings of this invention. What is illustrated and taught here isthat there are many applications requiring pattern recognitiontechnologies which can be achieved very economically through sharedpattern recognition computer facilities.

Since the cost of optical or camera systems have recently plummeted,this is now the technology of choice for occupant sensing. Such systemsare described in detail in the U.S. patents referenced under thissubject above. A single camera is, naturally, the least expensivesolution but suffers from the problem that there is no easy method ofobtaining three-dimensional information about people or objects that areoccupying the passenger compartment. A second camera can be added but tolocate the same objects or features in the two images by conventionalmethods is computationally intensive unless the two cameras are closetogether. If they are close together, however, then the accuracy of thethree dimensional information is compromised. Also, if they are notclose together, then the tendency is to add separate illumination foreach camera. An alternate solution is to use two cameras located atdifferent positions in the passenger compartment but to use a singlelighting source. This source can be located adjacent to one camera tominimize the installation sites. Since the LED illumination is now moreexpensive than the imager, the cost of the second camera does not addsignificantly to the system cost. Correlation of features can then bedone using pattern recognition systems such as neural networks. Twocameras also provide a significant protection from blockage and one ormore additional cameras, with additional illumination, can be added toprovide almost complete blockage protection.

Although some implementations of an occupant sensing system has beenshown in FIGS. 26 and 26A, other types of transducers or measurementdevices could be used without deviating from the teachings of thisinvention including, for example, laser radar, stereo and other 3Dimaging techniques, radar, electric field, capacitance, weightdistribution etc. (see, e.g., U.S. patent application Ser. No.10/413,426).

In FIG. 27, an occupant position sensor arrangement 241, 242 located ina headrest 240 of an automobile seat is illustrated. Such a sensorarrangement 241, 242 can be used to automatically position the headrest240 for protection of occupants in rear impacts, as part of a system toautomatically adjust the position of the seat based on the morphology ofthe occupant, and to monitor the position of the head in the event of afrontal impact. In each case, the sensor may interface with the neuralnetwork computer system that is used for crash sensing. In the case ofrear impact protection, for example, the neural computer, usinginformation from the accelerometers, may determine that a rear impact isin progress and command the headrest to move closer to the occupant'shead. If an anticipatory sensor is used for predicting a rear impact,the neural computer can be used to identify the approaching object anddecide if positioning the headrest is warranted. When the longitudinalposition of the occupant's head is monitored, then the neural crashsensor would take this into account along with other occupant positioninformation, if available, when determining whether to deploy the airbagif the occupant is out-of-position.

Other sensors which can be added to this system include those whichmeasure the position of the seat, position of the seat back, weight ofthe occupant, height of the occupant, seatbelt spool out, seatbeltbuckle engagement etc. The headrest position adjustment can beaccomplished in a number of ways including motors and an associatedmechanism such as a four-bar or other linkage.

4.3 Controlling Airbag Inflation

A schematic of an airbag gas control system in illustrated in FIG. 28and follows the description presented above. Data from the occupant,accelerometer(s), gyroscope(s), if present, and anticipatory sensor(s)are fed into the control module which controls one or more of: (i) thequantity of gas produced by the gas generator, (ii) the flow of the gasfrom the gas generator into the airbag or, alternately, the flow of aportion of the gas from the gas generator to the atmosphere before itenters the airbag, and (iii) the flow of the gas out of the airbag intothe atmosphere.

One issue that remains to be discussed is to derive the relationshipbetween the gas controller setting and the desired volume or quantity ofgas in the airbag. Generally, for a low velocity, long durationthreshold crash, for a small light weight out-of-position occupant, theairbag should be inflated slowly with a relatively small amount of gasand the outflow of gas from the airbag should be controlled so a minimumvalue constant pressure is maintained as the occupant just contacts thevehicle interior at the end of the crash.

Similarly, for a high velocity crash with large heavy occupant,positioned far from the airbag before deployment is initiated, but witha significant forward relative velocity due to pre-crash braking, theairbag should be deployed rapidly with a high internal pressure and anoutflow control which maintains a high pressure in the airbag as theoccupant exhausts the airbag to the point where he almost contacts theinterior vehicle surfaces at the end of the crash. These situations arequite different and require significantly different flow rates intoand/or out of the airbag. As crash variability is introduced such aswhere a vehicle impacts a pole in front of a barrier, the gas flowdecisions may be changed during the crash.

The neural network crash sensor has the entire history of the crash ateach point in time and therefore knows what instructions it gave to thegas controller during previous portions of the crash. It therefore knowswhat new instructions to give the controller to account for newinformation. The problem is to determine the controller function whenthe occupant parameters and crash-forecasted severity are known. Thisrequires the use of an occupant crash simulation program such as Madymo™from TNO in Delft, The Netherlands, along with a model of the gascontrol module.

A series of simulations are run with various settings of thecontrollable parameters such as the gas generation rate, gas inflow andgasoutflow restriction until acceptable results are obtained and theresults stored for that particular crash and occupant situation. In eachcase, the goal may be to maintain a constant pressure within the airbagduring the crash once the initial deployment has occurred. Those resultsfor each point in time are converted to a number and that number is thedesired output of the neural network used during the training. A moreautomated approach is to couple the simulation model with the neuralnetwork training program so that the desired results for the trainingare generated automatically.

Thus, as a particular case is being prepared as a training vector, theMadymo program is run which automatically determines the settings forthe particular gas control module, through a trial and error process,and these settings are converted to a number and normalized, with thenormalized number becoming the desired output value of the output nodeof the neural network. The above discussion is for illustration purposesonly and there are many ways that the interface between the neuralnetwork system and the gas controller can be designed. The descriptionsabove have concentrated on the control of the gas flows into and out ofan airbag. Other parts of the occupant restraint system can also becontrolled in a similar manner as the gas flows are controlled. Inparticular, various systems are now in use and others are beingdeveloped for controlling the force applied to the occupant by theseatbelt. In this case, it is desired to maintain a constantacceleration to the occupant depending on the crash severity. Suchsystems can use retractors or pretensioners, others use methods oflimiting the maximum force exerted by the seatbelt, while still othersapply damping or energy absorbing devices to provide a velocitysensitive force to the occupant.

A preferred approach, as disclosed in U.S. patent application Ser. No.10/413,426, uses a method of measuring the acceleration of the occupant,or some part such as his or her chest, and a mechanism that controls thespool out of the seatbelt to maintain the chest acceleration, forexample, to an appropriate limit such as 40 Gs. To the extent that thesesystems can be actively controlled by the restraint system based on thepattern recognition techniques described herein, they are contemplatedby this invention.

Also, the crash accelerometer(s), gyroscopes and occupant sensors havebeen the main inputs to the pattern recognition system as describedabove. This invention also contemplates the use of other availableinformation such as seatbelt use, seat position, seat back position,vehicle velocity etc. as additional inputs into the pattern recognitionsystem for particular applications depending on the availability of suchinformation.

4.4 Diagnostics

For a variety of reasons, placement of electronic components in or nearthe airbag module is desirable. Placement of the occupant sensing aswell as the diagnostics electronics within or adjacent to the airbagmodule has advantages to solving several current airbag problems. Forexample, there have been numerous inadvertent airbag deployments causedby wires in the system becoming shorted. Then, when the vehicle hits apothole, which is sufficient to activate the arming sensor or otherwisedisturb the sensing system, the airbag deploys. Such an unwanteddeployment of course can directly injure an occupant who isout-of-position or cause an accident that results in occupant injuries.If the sensor were to send a coded signal to the airbag module ratherthan a DC voltage with sufficient power to trigger the airbag, and ifthe airbag module had stored within its electronic circuit sufficientenergy to initiate the inflator, then these unwanted deployments wouldbe prevented. A shorted wire cannot send a coded signal and the shortcan be detected by the module resident diagnostic circuitry.

This makes it desirable for the airbag module contain the backup powersupply which further improves the reliability of the system since theelectrical connection to the sensor, or to the vehicle power, can nowpartially fail, as might happen during an accident, and the system willstill work properly. It is well known that the electrical resistance inthe “clockspring” connection system, which connects the steering wheelmounted airbag module to the sensor and diagnostic system, is marginalin design and prone to failure. The resistance of this electricalconnection must be very low or there will not be sufficient power toreliably initiate the inflator squib. To reduce the resistance to thelevel required, high quality gold plated connectors are used and thewires must also be of unusually high quality. Due to space constraints,however, these wires have only a marginally adequate resistance therebyreducing the reliability of the driver airbag module and increasing itscost. If, on the other hand, the power to initiate the airbag werealready in the module, then only a coded signal need be sent to themodule rather than sufficient power to initiate the inflator. Thus, theresistance problem disappears and the module reliability is increased.Additionally, the requirements for the clockspring wires become lesssevere and the design can be relaxed reducing the cost and complexity ofthe device. It may even be possible to return to the slip ring systemthat existed prior to the implementation of airbags.

Under this system, the power supply can be charged over a few seconds,since the power does not need to be sent to the module at the time ofthe required airbag deployment because it is already there. Thus, all ofthe electronics associated with the airbag system except the sensor andits associated electronics, if any, would be within or adjacent to theairbag module. This includes optionally the occupant sensor, thediagnostics and the backup power supply, which now becomes the primarypower supply, and the need for a backup disappears. When a fault isdetected a message is sent to a display unit located typically in theinstrument panel.

Placement of the main electronics within each module follows thedevelopment path that computers themselves have followed from a largecentralized mainframe base to a network of microcomputers. The computingpower required by an occupant position sensor, airbag system diagnosticsand backup power supply is greater than that required by a single pointsensor. For this reason, it is more logical to put this electronicpackage within or adjacent to each module. In this manner, theadvantages of a centralized single point sensor and diagnostic systemfade since most of the intelligence will reside within or adjacent tothe individual modules and not the centralized system. A simple and moreeffective CrushSwitch sensor such as disclosed in U.S. Pat. No.5,441,301, for example, now becomes more cost effective than the singlepoint sensor and diagnostic system which is now being widely adopted.Finally, this also is consistent with the migration to a bus systemwhere the power and information are transmitted around the vehicle on asingle bus system thereby significantly reducing the number of wires andthe complexity of the vehicle wiring system. The decision to deploy anairbag is sent to the airbag module sub-system as a signal not as aburst of power. Although it has been assumed that the information wouldbe sent over a wire bus, it is also possible to send the deploy commandby a variety of wireless methods.

A partial implementation of the system as just described is depictedschematically in FIG. 67 which shows a view of the combination of anoccupant position sensor and airbag module designed to prevent thedeployment of the airbag for a seat which is unoccupied or if theoccupant is too close to the airbag and therefore in danger ofdeployment induced injury. The module, shown generally at 550, includesa housing which comprises an airbag 551, an inflator assembly 552 forthe airbag 551, an occupant position sensor comprising an ultrasonictransmitter 553 and an ultrasonic receiver 554. Other occupant positionsensors can also be used instead of the ultrasonic transmitter/receiverpair to determine the position of the occupant to be protected by theairbag 551, and also the occupant position sensor may be located outsideof the housing of the module 550. The housing of the module 550 alsocontains an electronic module or package 555 coupled to each of theinflator assembly 552, the transmitter 553 and the receiver 554 andwhich performs the functions of sending the ultrasonic signal to thetransmitter 553 and processing the data from the occupant positionsensor receiver 554. Electronics module 555 may be arranged within thehousing of the module 550 as shown or adjacent or proximate the housingof the module 550. Module 550 also contains a power supply (not shown)for supplying power upon command by the electronics module 555 to theinflator assembly 552 to cause inflation of the airbag 551. Thus,electronics module 555 controls the inflation or deployment of theairbag 551 and may sometimes herein be referred to as a controller orcontrol unit. In addition, the electronic module 555 monitors the powersupply voltage, to assure that sufficient energy is stored to initiatethe inflator assembly 552 when required, and power the other processes,and reports periodically over the vehicle bus 556 to the centraldiagnostic module, shown schematically at 557, to indicate that themodule is ready, i.e., there is sufficient power of inflate or deploythe airbag 551 and operate the occupant position sensortransmitter/receiver pair, or sends a fault code if a failure in anycomponent being monitored has been detected. A CrushSwitch sensor isalso shown schematically at 558, which is the only discriminating sensorin the system. Sensor 558 is coupled to the vehicle bus 556 andtransmits a coded signal over the bus to the electronics module 555 tocause the electronics module 555 to initiate deployment of the airbag551 via the inflator assembly 552. The vehicle bus 556 connects theelectronic package 555, the central sensor and diagnostic module 557 andthe CrushSwitch sensor 558. Bus 556 may be the single bus system, i.e.,consists of a pair of wires, on which power and information aretransmitted around the vehicle as noted immediately above. Instead ofCrushSwitch sensor 558, other crash sensors may be used.

When several crash sensors and airbag modules are present in thevehicle, they can all be coupled to the same bus or discrete portions ofthe airbag modules and crash sensors can be coupled to separate buses.Other ways for connecting the crash sensors and airbag modules to anelectrical bus can also be implemented in accordance with the inventionsuch as connecting some of the sensors and/or modules in parallel to abus and others daisy-chained into the bus. This type of bus architectureis described in U.S. Pat. No. 6,212,457, incorporated by referenceherein.

It should be understood that airbag module 550 is a schematicrepresentation only and thus, may represent any of the airbag modulesdescribed above in any of the mounting locations. For example, airbagmodule 550 may be arranged in connection with the seat 478 as module 477is in FIG. 59. As such, the bus, which is connected to the airbag module550, would inherently extend at least partially into and within theseat.

Another implementation of the invention incorporating the electroniccomponents into and adjacent to the airbag module as illustrated in FIG.68 which shows the interior front of the passenger compartment generallyat 560. Driver airbag module 561 is partially cutaway to show anelectronic module 562 incorporated within the airbag module 561.Electronic module 562 may be comparable to electronic module 555 in theembodiment of FIG. 67 in that it can control the deployment of theairbag in airbag module 561. Electronic airbag module 561 is connectedto an electronic sensor illustrated generally as 566 by wire 563. Theelectronic sensor 566 is, e.g., an electronic single point crash sensorthat initiates the deployment of the airbag when it senses a crash.Passenger airbag module 565 is illustrated with its associatedelectronic module 567 outside of but adjacent or proximate to the airbagmodule. Electronic module 567 may be comparable to electronic module 555in the embodiment of FIG. 67 in that it can control the deployment ofthe airbag in airbag module 565. Electronic module 567 is connected by awire 564, which could also be part of a bus, to the electronic sensor566. One or both of the electronic modules 562, 567 can containdiagnostic circuitry, power storage capability (either a battery or acapacitor), occupant sensing circuitry, as well as communicationelectronic circuitry for either wired or wireless communication.

It should be understood that although only two airbag modules 561, 565are shown, it is envisioned that an automotive safety network may bedesigned with several and/or different types of occupant protectiondevices. Such an automotive network would comprises one or more occupantprotection devices connected to the bus, each comprising a housing and acomponent deployable to provide protection for the occupant, at leastone sensor system for providing an output signal relevant to deploymentof the deployable component(s) (such as the occupant sensing circuitry),a deployment determining system for generating a signal indicating forwhich of the deployable components deployment is desired (such as acrash sensor) and an electronic controller arranged in, proximate oradjacent each housing and coupled to the sensor system(s) and thedeployment determining system. The electrical bus electrically couplesthe sensor system(s), the deployment determining system and thecontrollers so that the signals from one or more of the sensor systemsand the deployment determining system are sent over the bus to thecontrollers. Each controller controls deployment of the deployablecomponent of the respective occupant protection device in considerationof the signals from the sensor system(s) and the deployment determiningsystem. The crash sensor(s) may be arranged separate and at a locationapart from the housings and generate a coded signal when deployment ofany one of the deployable components is desired. Thus, the coded signalvaries depending on which of deployment components are to be deployed.If the deployable component is an airbag associated with the housing,the occupant protection device would comprise an inflator assemblyarranged in the housing for inflating the airbag.

Several technologies have been described above all of which have theobjective of improving the reliability and reducing the complexity ofthe wiring system in an automobile and particularly the safety system.Most importantly the bus technology described has as its objectivesimplification and increase in reliability of the vehicle wiring system.This wiring system was first conceived of as a method of permitting thelocation of airbag crash sensors at locations where they can mosteffectively sense a vehicle crash and yet permit that information to betransmitted to airbag control circuitry which may be located in aprotective portion of the interior of the vehicle or may even be locatedon the airbag module itself. To protect this affirmation transmissionrequires a wiring system that is far more reliable and resistant tobeing destroyed in the vary crash that the sensor is sensing. This ledto the realization that the data bus that carries the information fromthe crash sensor must be particularly reliable. Upon designing such adata bus, however, it was found that the capacity of that data bus farexceeded the needs of the crash sensor system. This then led to arealization that the capacity, or bandwidth, of such a bus would besufficient to carry all of the vehicle information requirements. In somecases this requires the use of high bandwidth bus technology such astwisted pair wires, shielded twisted pair wires, or coax cable. If asubset of all of the vehicle devices is included on the bus, then thebandwidth requirements are less and simpler bus technologies can be usedin place of the coax cable, for example. The economics that accompany adata bus design which has the highest reliability, highest bandwidth, isjustified if all of the vehicle devices use the same system. This iswhere the greatest economies and greatest reliability occur. Asdescribed above, this permits, for example, placement of the airbagfiring electronics into the same housing that contains the airbaginflator. Once the integrity of the data bus is assured, such that itwill not be destroyed during the crash itself, then the proper place forthe airbag intelligence is in the airbag module itself. This furtherproves the reliability of the system since the shorting of the wires tothe airbag module will not inadvertently set off the airbag as hashappened frequently in the past.

When operating on the vehicle data bus, each device should have a uniqueaddress and each associated device must know that address. For mostsituations, therefore, this address must be predetermined and theassigned through an agreed-upon standard for all vehicles. Thus, theleft rear tail light must have a unique address so that when the turnsignal is turned to flash that light it does not also flash the righttail light, for example. Similarly, the side impact crash sensor whichwill operate on the same data bus as the frontal impact crash sensor,must issue a command to the side impact airbag and not to the frontalimpact airbag.

One of the key advantages of a single bus system connecting all sensorsin the vehicle together is the possibility of using this data bus todiagnose the health of the entire vehicle, as described in the detailabove. Thus, we can see the synergistic advantages of all the disparatetechnologies described above.

The design, construction, installation, and maintenance a vehicle databus network requires attention to many issues, including: an appropriatecommunication protocol, physical layer transceivers for the selectedmedia, capable microprocessors for both application and protocolexecution, device controller hardware & software for the requiredsensors and actuators, etc. Such activities are known to those skilledin the art and will not be described in detail here.

An intelligent distributed system as described above can be based on theCAN Protocol, for example, which is a common protocol used in theautomotive industry. CAN is a full function network protocol thatprovides both message checking and correction to insure communicationintegrity. Many of the devices on the system will have specialdiagnostics designed into them. For instance, some of the inflatorcontrols can send warning messages if their backup power supply hasinsufficient charge. In order to assure the integrity and reliability ofthe bus system, most devices will be equipped with bi-directionalcommunication as described above. Thus, when a message is sent to therear right taillight to turn on, the light can return a message that ithas executed the instruction.

A smart airbag system is really part of a general vehicle diagnosticsystem and many of the components that make up the airbag system and therest of the vehicle diagnostic system can be shared. Therefore, we willnow briefly discuss a general vehicle diagnostic system focusing on theinteraction with the occupant restraint system. This description istaken from U.S. Pat. No. 6,484,080.

For the purposes herein the following terms are defined as follows:

The term “component” refers to any part or assembly of parts that ismounted to or a part of a motor vehicle and which is capable of emittinga signal representative of its operating state that can be sensed by anyappropriate sensor. The following is a partial list of generalautomobile and truck components, the list not being exclusive:

Occupant restraints; engine; transmission; brakes and associated brakeassembly; tires; wheel; steering wheel and steering column assembly;water pump; alternator; shock absorber; wheel mounting assembly;radiator; battery; oil pump; fuel pump; air conditioner compressor;differential gear; exhaust system; fan belts; engine valves; steeringassembly; vehicle suspension including shock absorbers; vehicle wiringsystem; and engine cooling fan assembly.

The term “sensor” as used herein will generally refer to any measuring,detecting or sensing device mounted on a vehicle or any of itscomponents including new sensors mounted in conjunction with thediagnostic module in accordance with the invention. A partial,non-exhaustive list of common sensors mounted on an automobile or truckis:

airbag crash sensor; accelerometer; microphone; camera; antenna;capacitance sensor or other electromagnetic wave sensor; stress orstrain sensor; pressure sensor; weight sensor; magnetic field or fluxsensor; coolant thermometer; oil pressure sensor; oil level sensor; airflow meter; voltmeter; ammeter; humidity sensor; engine knock sensor;oil turbidity sensor; throttle position sensor; steering wheel torquesensor; wheel speed sensor; tachometer; speedometer; other velocitysensors; other position or displacement sensors; oxygen sensor; yaw,pitch and roll angular sensors; clock; odometer; power steering pressuresensor; pollution sensor; fuel gauge; cabin thermometer; transmissionfluid level sensor; gyroscopes or other angular rate sensors includingyaw, pitch and roll rate sensors; coolant level sensor; transmissionfluid turbidity sensor; break pressure sensor; tire pressure sensor;tire temperature sensor; tire acceleration sensor; GPS receiver; DGPSreceiver; coolant pressure sensor; occupant position sensor; andoccupant weight sensor.

The term “actuator” as used herein will generally refer to a device thatperforms some action upon receiving the proper signal. Examples ofactuators include:

window motor; door opening and closing motor; electric door lock; decklid lock; airbag inflator initiator; fuel injector; brake valves; pumps;relays; and steering assist devices.

The term “signal” as used herein will generally refer to any timevarying output from a component including electrical, acoustic, thermal,or electromagnetic radiation, or mechanical vibration.

Sensors on a vehicle are generally designed to measure particularparameters of particular vehicle components. However, frequently thesesensors also measure outputs from other vehicle components. For example,electronic airbag crash sensors currently in use contain anaccelerometer for determining the accelerations of the vehicle structureso that the associated electronic circuitry of the airbag crash sensorcan determine whether a vehicle is experiencing a crash of sufficientmagnitude so as to require deployment of the airbag.

An IMU using up to three accelerometers and up to three gyroscopes canalso be used. This accelerometer continuously monitors the vibrations inthe vehicle structure regardless of the source of these vibrations. If awheel is out-of-balance or delaminating, or if there is extensive wearof the parts of the front wheel mounting assembly, or wear in the shockabsorbers, the resulting abnormal vibrations or accelerations can, inmany cases, be sensed by the crash sensor accelerometer. There are othercases, however, where the sensitivity or location of the airbag crashsensor accelerometer is not appropriate and one or more additionalaccelerometers and/or gyroscopes or IMU may be mounted onto a vehiclefor the purposes of this invention. Some airbag crash sensors are notsufficiently sensitive accelerometers or have sufficient dynamic rangefor the purposes herein.

Every component of a vehicle emits various signals during its life.These signals can take the form of electromagnetic radiation, acousticradiation, thermal radiation, electric or magnetic field variations,vibrations transmitted through the vehicle structure, and voltage orcurrent fluctuations, depending on the particular component. When acomponent is functioning normally, it may not emit a perceptible signal.In that case, the normal signal is no signal, i.e., the absence of asignal. In most cases, a component will emit signals that change overits life and it is these changes that contain information as to thestate of the component, e.g., whether failure of the component isimpending. Usually components do not fail without warning. However, mostsuch warnings are either not perceived or if perceived are notunderstood by the vehicle operator until the component actually failsand, in some cases, a breakdown of the vehicle occurs. In a few years,it is expected that various roadways will have systems for automaticallyguiding vehicles operating thereon. Such systems have been called “smarthighways” and are part of the field of intelligent transportationsystems (ITS). If a vehicle operating on such a smart highway were tobreakdown, serious disruption of the system could result and the safetyof other users of the smart highway could be endangered.

As discussed in detail above, accelerometers are routinely used mountedoutside of the crush zone for sensing the failure of the vehicle, thatis, a crash of the vehicle. Looking at this in general terms, there issynergy between the requirements of sensing the status of the wholevehicle as well as its components and the same sensors can often be usedfor multiple purposes. The output of a microphone mounted in the vehiclecould be used to help determine the existence and severity of a crash,for example.

In accordance with the invention, each of these signals emitted by thevehicle components is converted into electrical signals and thendigitized (i.e., the analog signal is converted into a digital signal)to create numerical time series data that is then entered into aprocessor. Pattern recognition algorithms are then applied in theprocessor to attempt to identify and classify patterns in this timeseries data. For a particular component, such as a tire for example, thealgorithm attempts to determine from the relevant digital data whetherthe tire is functioning properly and/or whether it requires balancing,additional air, or perhaps replacement. Future systems may bypass theA/D conversion and operate directly on the analog signals. Opticalcorrelation systems are now used by the military that create the Fouriertransform of an image directly using diffraction gratings and comparethe image with a stored image.

Frequently, the data entered into the computer needs to be pre-processedbefore being analyzed by a pattern recognition algorithm. The data froma wheel speed sensor, for example, might be used as is for determiningwhether a particular tire is operating abnormally in the event it isunbalanced, whereas the integral of the wheel speed data over a longtime period (integration being a pre-processing step), when compared tosuch sensors on different wheels, might be more useful in determiningwhether a particular tire is going flat and therefore needs air.

In some cases, the frequencies present in a set of data are a betterpredictor of component failures than the data itself. For example, whena motor begins to fail due to worn bearings, certain characteristicfrequencies began to appear. In most cases, the vibrations arising fromrotating components, such as the engine, will be normalized based on therotational frequency as disclosed in a recent NASA TSP. Moreover, theidentification of which component is causing vibrations present in thevehicle structure can frequently be accomplished through a frequencyanalysis of the data. For these cases, a Fourier transformation of thedata is made prior to entry of the data into a pattern recognitionalgorithm. As mentioned above, optical correlations systems usingFourier transforms can also be applicable.

Other mathematical transformations are also made for particular patternrecognition purposes in practicing the teachings of this invention. Someof these include shifting and combining data to determine phase changesfor example, differentiating the data, filtering the data, and samplingthe data. Also, there exist certain more sophisticated mathematicaloperations that attempt to extract or highlight specific features of thedata. This invention contemplates the use of a variety of thesepreprocessing techniques, and combinations thereof, and the choice ofwhich one or ones is left to the skill of the practitioner designing aparticular diagnostic module.

Another technique that is contemplated for some implementations of thisinvention is the use of multiple accelerometers and/or microphones thatallow the system to locate the source of any measured vibrations basedon the time of flight, or time of arrival of a signal at differentlocations, and/or triangulation techniques. Once a distributedaccelerometer installation has been implemented to permit this sourcelocation, the same sensors can be used for smarter crash sensing as itwill permit the determination of the location of the impact on thevehicle. Once the impact location is known, a highly tailored algorithmcan be used to accurately forecast the crash severity making use ofknowledge of the force vs. crush properties of the vehicle at the impactlocation.

When a vehicle component begins to change its operating behavior, it isnot always apparent from the particular sensors, if any, which aremonitoring that component. Output from any one of these sensors can benormal even though the component is failing. By analyzing the output ofa variety of sensors, however, the pending failure can be diagnosed. Forexample, the rate of temperature rise in the vehicle coolant, if it weremonitored, might appear normal unless it were known that the vehicle wasidling and not traveling down a highway at a high speed. Even the levelof coolant temperature which is in the normal range could in fact beabnormal in some situations signifying a failing coolant pump, forexample, but not detectable from the coolant thermometer alone.

Pending failure of some components is difficult to diagnose andsometimes the design of the component requires modification so that thediagnosis can be more readily made. A fan belt, for example, frequentlybegins failing by a cracking of the inner surface. The belt can bedesigned to provide a sonic or electrical signal when this crackingbegins in a variety of ways. Similarly, coolant hoses can be designedwith an intentional weak spot where failure will occur first in acontrolled manner that can also cause a whistle sound as a small amountof steam exits from the hose. This whistle sound can then be sensed by ageneral purpose microphone, for example.

A connector for joining two coaxial cables 36 and 37 is illustrated inFIGS. 69A, 69B, 69C and 69D generally as 35. A cover 35 a is hingablyattached to a base 38. A connector plate 40 is slidably inserted intobase 38 and contains two abrasion and connection sections 42 and 43. Asecond connecting plate 44 contains two connecting pins 41, onecorresponding to each cable to be connected. To connect the two cables36 and 37 together, they are first inserted into their respective holes45 and 46 in base 38 until they are engaged by pins 41. Slidingconnector plate 40 is then inserted and cover 40 a rotated pushingconnector plate 40 downward until the catch 47 snaps over mating catch48. Other latching arrangements are of course usable in accordance withthe invention. During this process, the serrated part 42 of connectorplate 45 abrades the insulating cover off of the outside of therespective cable exposing the outer conductor. The particle-coatedsection 43 of connector plate 40 then engages and makes electricalcontact with the outer conductor of the coaxial cables 36 and 37. Inthis manner, the two coaxial cables 36, 37 are electrically connectedtogether in a very simple manner.

In FIG. 29, a generalized component 250 emitting several signals thatare transmitted along a variety of paths, sensed by a variety of sensorsand analyzed by the diagnostic device in accordance with the inventionis illustrated schematically. Component 250 is mounted to a vehicle andduring operation, it emits a variety of signals such as acoustic 251,electromagnetic radiation 252, thermal radiation 253, current andvoltage fluctuations in conductor 254 and mechanical vibrations 255.Various sensors are mounted in the vehicle to detect the signals emittedby the component 250. These include one or more vibration sensors(accelerometers) 259, 261 and/or gyroscopes also mounted to the vehicle,one or more acoustic sensors 256, 262, electromagnetic radiation sensor257, heat radiation sensor 258, and voltage or current sensor 260. Inaddition, various other sensors 263, 264 measure other parameters ofother components that in some manner provide information directly orindirectly on the operation of component 250.

All of the sensors illustrated on FIG. 29 can be connected to a data bus265. A diagnostic module 266, in accordance with the invention, can alsobe attached to the vehicle data bus 265 and receives the signalsgenerated by the various sensors. The sensors may however be wirelesslyconnected to the diagnostic module 266 and be integrated into a wirelesspower and communications system or a combination of wired and wirelessconnections.

As shown in FIG. 29, the diagnostic module 266 has access to the outputdata of each of the sensors that have potential information relative tothe component 250. This data appears as a series of numerical valueseach corresponding to a measured value at a specific point in time. Thecumulative data from a particular sensor is called a time series ofindividual data points. The diagnostic module 266 compares the patternsof data received from each sensor individually, or in combination withdata from other sensors, with patterns for which the diagnostic module266 has been trained to determine whether the component 250 isfunctioning normally or abnormally. Note that although a general vehiclecomponent diagnostic system is being described, the state of somevehicle components can provide information to the vehicle safety system.A tire failure, for example, can lead to a vehicle rollover.

Important to this invention is the manner in which the diagnostic module266 determines a normal pattern from an abnormal pattern and the mannerin which it decides what data to use from the vast amount of dataavailable. This is accomplished using pattern recognition technologiessuch as artificial neural networks and training. The theory of neuralnetworks including many examples can be found in several books on thesubject as discussed above. The neural network pattern recognitiontechnology is one of the most developed of pattern recognitiontechnologies. The neural network will be used here to illustrate oneexample of a pattern recognition technology but it is emphasized thatthis invention is not limited to neural networks. Rather, the inventionmay apply any known pattern recognition technology including sensorfusion and various correlation technologies. A brief description of theneural network pattern recognition technology is set forth below.

Neural networks are constructed of processing elements known as neuronsthat are interconnected using information channels call interconnects.Each neuron can have multiple inputs but generally only one output. Eachoutput however is connected to all other neurons in the next layer.Neurons in the first layer operate collectively on the input data asdescribed in more detail below. Neural networks learn by extractingrelational information from the data and the desired output. Neuralnetworks have been applied to a wide variety of pattern recognitionproblems including automobile occupant sensing, speech recognition,optical character recognition, and handwriting analysis.

To train a neural network, data is provided in the form of one or moretime series that represents the condition to be diagnosed as well asnormal operation. As an example, the simple case of an out-of-balancetire will be used. Various sensors on the vehicle can be used to extractinformation from signals emitted by the tire such as an accelerometer, atorque sensor on the steering wheel, the pressure output of the powersteering system, a tire pressure monitor or tire temperature monitor.Other sensors that might not have an obvious relationship to anunbalanced tire are also included such as, for example, the vehiclespeed or wheel speed. Data is taken from a variety of vehicles where thetires were accurately balanced under a variety of operating conditionsalso for cases where varying amounts of unbalance was intentionallyintroduced. Once the data has been collected, some degree ofpreprocessing or feature extraction is usually performed to reduce thetotal amount of data fed to the neural network. In the case of theunbalanced tire, the time period between data points might be chosensuch that there are at least ten data points per revolution of thewheel. For some other application, the time period might be one minuteor one millisecond.

Once the data has been collected, it is processed by a neuralnetwork-generating program, for example, if a neural network patternrecognition system is to be used. Such programs are availablecommercially, e.g., from NeuralWare of Pittsburgh, Pa. The programproceeds in a trial and error manner until it successfully associatesthe various patterns representative of abnormal behavior, an unbalancedtire, with that condition. The resulting neural network can be tested todetermine if some of the input data from some of the sensors, forexample, can be eliminated. In this way, the engineer can determine whatsensor data is relevant to a particular diagnostic problem. The programthen generates an algorithm that is programmed onto a microprocessor,microcontroller, neural processor, or DSP (herein collectively referredto as a microprocessor or processor). Such a microprocessor appearsinside the diagnostic module 266 in FIG. 29.

Once trained, the neural network, as represented by the algorithm, willnow operationally recognize an unbalanced tire on a vehicle when thisevent occurs. At that time, when the tire is unbalanced, the diagnosticmodule 266 will output a signal indicative of the unbalanced tire, suchas a signal to be sent to an output device which provides a message tothe driver indicating that the tire should be now be balanced asdescribed in more detail below. The message to the driver is provided byan output device coupled to or incorporated within the module 266 andmay be, e.g., a light on the dashboard, a vocal tone or any otherrecognizable indication apparatus. Messages can also be transmitter toothers outside of the vehicle such as other vehicles or to a vehicledealer. In some cases, control of the vehicle may be taken over by avehicle system in response to a message. In some cases, the vehiclecomponent failure portends an oncoming accident and one or more parts ofthe restraint system can be deployed.

It is important to note that there may be many neural networks involvedin a total vehicle diagnostic system. These can be organized either inparallel, series, as an ensemble, cellular neural network or as amodular neural network system. In one implementation of a modular neuralnetwork, a primary neural network identifies that there is anabnormality and tries to identify the likely source. Once a choice hasbeen made as to the likely source of the abnormality, another of a groupof neural networks is called upon to determine the exact cause of theabnormality. In this manner, the neural networks are arranged in a treepattern with each neural network trained to perform a particular patternrecognition task.

Discussions on the operation of a neural network can be found in theabove references on the subject and are well understood by those skilledin the art. Neural networks are the most well-known of the patternrecognition technologies based on training, although neural networkshave only recently received widespread attention and have been appliedto only very limited and specialized problems in motor vehicles. Othernon-training based pattern recognition technologies exist, such as fuzzylogic. However, the programming required to use fuzzy logic, where thepatterns must be determined by the programmer, render these systemsimpractical for general vehicle diagnostic problems such as describedherein. Therefore, preferably the pattern recognition systems that learnby training are used herein. On the other hand, the combination ofneural networks and fuzzy logic, such as in a Neural-Fuzzy system, areapplicable and can result in superior results.

The neural network is the first highly successful of what will be avariety of pattern recognition techniques based on training. There isnothing that suggests that it is the only or even the best technology.The characteristics of all of these technologies which render themapplicable to this general diagnostic problem include the use oftime-based input data and that they are trainable. In all cases, thepattern recognition technology learns from examples of datacharacteristic of normal and abnormal component operation.

A diagram of one example of a neural network used for diagnosing anunbalanced tire, for example, based on the teachings of this inventionis shown in FIG. 2 (discussed above). The process can be programmed toperiodically test for an unbalanced tire. Since this need be done onlyinfrequently, the same processor can be used for many such diagnosticproblems. When the particular diagnostic test is run, data from thepreviously determined relevant sensors is preprocessed and analyzed withthe neural network algorithm. For the unbalanced tire, using the datafrom an accelerometer for example, the digital acceleration values fromthe analog to digital converter in the accelerometer are entered intonodes 1 through n and the neural network algorithm compares the patternof values on nodes 1 through n with patterns for which it has beentrained as follows.

Each of the input nodes is connected to each of the second layer nodes,h-1, h-2, . . . , h-n, called the hidden layer, either electrically asin the case of a neural computer, or through mathematical functionscontaining multiplying coefficients called weights, in the mannerdescribed in more detail in the above references. At each hidden layernode, a summation occurs of the values from each of the input layernodes, which have been operated on by functions containing the weights,to create a node value. Similarly, the hidden layer nodes are in likemanner connected to the output layer node(s), which in this example isonly a single node 0 representing the decision to notify the driver ofthe unbalanced tire. During the training phase, an output node value of1, for example, is assigned to indicate that the driver should benotified and a value of 0 is assigned to not providing an indication tothe driver. Once again, the details of this process are described inabove-referenced texts and will not be presented in detail here.

In the example above, twenty input nodes were used, five hidden layernodes and one output layer node. In this example, only one sensor wasconsidered and accelerations from only one direction were used. If otherdata from other sensors such as accelerations from the vertical orlateral directions were also used, then the number of input layer nodeswould increase. Again, the theory for determining the complexity of aneural network for a particular application has been the subject of manytechnical papers and will not be presented in detail here. Determiningthe requisite complexity for the example presented here can beaccomplished by those skilled in the art of neural network design. Foran example of the use of a neural network crash sensor algorithm, seeU.S. Pat. No. 5,684,701. Note that the inventors of this inventioncontemplate all combinations of the teachings of the '701 patent andthose disclosed herein.

It is also possible to apply modular neural networks in accordance withthe invention wherein several neural network are trained, each having aspecific function relating to the detection of the abnormality in theoperation of the component. The particular neural network(s) used, i.e.,those to which input is provided or from which output is used, can bedetermined based on the measurements by one or more of the sensors.

Briefly, the neural network described above defines a method, using apattern recognition system, of sensing an unbalanced tire anddetermining whether to notify the driver and comprises:

(a) obtaining an acceleration signal from an accelerometer mounted on avehicle;

(b) converting the acceleration signal into a digital time series;

(c) entering the digital time series data into the input nodes of theneural network;

(d) performing a mathematical operation on the data from each of theinput nodes and inputting the operated on data into a second series ofnodes wherein the operation performed on each of the input node dataprior to inputting the operated on value to a second series node isdifferent from (e.g. may employ a different weight) that operationperformed on some other input node data;

(e) combining the operated on data from all of the input nodes into eachsecond series node to form a value at each second series node;

(f) performing a mathematical operation on each of the values on thesecond series of nodes and inputting this operated on data into anoutput series of nodes wherein the operation performed on each of thesecond series node data prior to inputting the operated on value to anoutput series node is different from that operation performed on someother second series node data;

(g) combining the operated on data from all of the second series nodesinto each output series node to form a value at each output series node;and

(h) notifying a driver or taking some other action if the value on oneoutput series node is within a selected range signifying that a tirerequires balancing.

This method can be generalized to a method of predicting that acomponent of a vehicle will fail comprising:

(a) sensing a signal emitted from the component;

(b) converting the sensed signal into a digital time series;

(c) entering the digital time series data into a pattern recognitionalgorithm;

(d) executing the pattern recognition algorithm to determine if thereexists within the digital time series data a pattern characteristic ofabnormal operation of the component; and

(e) notifying a driver or taking some other action, including, in somecases, deployment of an occupant restraint system, if the abnormalpattern is recognized.

The particular neural network described above contains a single seriesof hidden layer nodes. In some network designs, more than one hiddenlayer is used, although only rarely will more than two such layersappear. There are of course many other variations of the neural networkarchitecture illustrated above which appear in the referencedliterature. For the purposes herein, therefore, “neural network” will bedefined as a system wherein the data to be processed is separated intodiscrete values which are then operated on and combined in at least atwo-stage process and where the operation performed on the data at eachstage is, in general, different for each discrete value and where theoperation performed is at least determined through a training process.

Implementation of neural networks can take on at least two forms, analgorithm programmed on a digital microprocessor, DSP or in a neuralcomputer. In this regard, it is noted that neural computer chips are nowbecoming available.

In the example above, only a single component failure was discussedusing only a single sensor since the data from the single sensorcontains a pattern which the neural network was trained to recognize aseither normal operation of the component or abnormal operation of thecomponent. The diagnostic module 266 contains preprocessing and neuralnetwork algorithms for a number of component failures. The neuralnetwork algorithms are generally relatively simple, requiring only a fewhundred lines of computer code. A single general neural network programcan be used for multiple pattern recognition cases by specifyingdifferent coefficients for various terms, one set for each application.Thus, adding different diagnostic checks has only a small affect on thecost of the system. Also, the system has available to it all of theinformation available on the data bus. During the training process, thepattern recognition program sorts out from the available vehicle data onthe data bus or from other sources, those patterns that predict failureof a particular component. Sometimes more than one data bus is used. Forexample, in some cases, there is a general data bus and one reserved forsafety systems. Any number of data buses can of course be monitored.

In FIG. 30, a schematic of a vehicle with several components and severalsensors in their approximate locations on a vehicle is shown along witha total vehicle diagnostic system in accordance with the inventionutilizing a diagnostic module in accordance with the invention. A flowdiagram of information passing from the various sensors shown on FIG. 30onto a vehicle data bus and thereby into the diagnostic device inaccordance with the invention is shown in FIG. 31 along with outputs toa display 278 for notifying the driver and/or to the vehicle cellularphone 279, or other communication device, for notifying the dealer,vehicle manufacturer or other entity concerned with the failure of acomponent in the vehicle including the vehicle itself such as occurs ina crash. If the vehicle is operating on a smart highway, for example,the pending component failure information may also be communicated to ahighway control system and/or to other vehicles in the vicinity so thatan orderly exiting of the vehicle from the smart highway can befacilitated. FIG. 31 also contains the names of the sensors shownnumbered on FIG. 30.

Sensor 1 is a crash sensor having an accelerometer (alternately one ormore dedicated accelerometers can be used), sensor 2 is represents oneor more microphones, sensor 3 is a coolant thermometer, sensor 4 is anoil pressure sensor, sensor 5 is an oil level sensor, sensor 6 is an airflow meter, sensor 7 is a voltmeter, sensor 8 is an ammeter, sensor 9 isa humidity sensor, sensor 10 is an engine knock sensor, sensor 11 is anoil turbidity sensor, sensor 12 is a throttle position sensor, sensor 13is a steering torque sensor, sensor 14 is a wheel speed sensor, sensor15 is a tachometer, sensor 16 is a speedometer, sensor 17 is an oxygensensor, sensor 18 is a pitch/roll sensor, sensor 19 is a clock, sensor20 is an odometer, sensor 21 is a power steering pressure sensor, sensor22 is a pollution sensor, sensor 23 is a fuel gauge, sensor 24 is acabin thermometer, sensor 25 is a transmission fluid level sensor,sensor 26 is a yaw sensor, sensor 27 is a coolant level sensor, sensor28 is a transmission fluid turbidity sensor, sensor 29 is brake pressuresensor and sensor 30 is a coolant pressure sensor. Other possiblesensors include a temperature transducer, a pressure transducer, aliquid level sensor, a flow meter, a position sensor, a velocity sensor,a RPM sensor, a chemical sensor and an angle sensor, angular rate sensoror gyroscope.

If a distributed group of acceleration sensors or accelerometers areused to permit a determination of the location of a vibration source,the same group can, in some cases, also be used to measure the pitch,yaw and/or roll of the vehicle eliminating the need for dedicatedangular rate sensors. In addition, as mentioned above, such a suite ofsensors can also be used to determine the location and severity of avehicle crash and additionally to determine that the vehicle is on theverge of rolling over. Thus, the same suite of accelerometers optimallyperforms a variety of functions including inertial navigation, crashsensing, vehicle diagnostics, roll over sensing etc.

Consider now some examples. The following is a partial list of potentialcomponent failures and the sensors from the list on FIG. 31 that mightprovide information to predict the failure of the component:

Vehicle crash 1, 2, 14, 16, 18, 26, 31, 32, 33 Vehicle Rollover 1, 2,14, 16, 18, 26, 31, 32, 33 Out of balance tires 1, 13, 14, 15, 20, 21Front end out of alignment 1, 13, 21, 26 Tune up required 1, 3, 10, 12,15, 17, 20, 22 Oil change needed 3, 4, 5, 11 Motor failure 1, 2, 3, 4,5, 6, 10, 12, 15, 17, 22 Low tire pressure 1, 13, 14, 15, 20, 21 Frontend looseness 1, 13, 16, 21, 26 Cooling system failure 3, 15, 24, 27, 30Alternator problems 1, 2, 7, 8, 15, 19, 20 Transmission problems 1, 3,12, 15, 16, 20, 25, 28 Differential problems 1, 12, 14 Brakes 1, 2, 14,18, 20, 26, 29 Catalytic converter and muffler 1, 2, 12, 15, 22 Ignition1, 2, 7, 8, 9, 10, 12, 17, 23 Tire wear 1, 13, 14, 15, 18, 20, 21, 26Fuel leakage 20, 23 Fan belt slippage 1, 2, 3, 7, 8, 12, 15, 19, 20Alternator deterioration 1, 2, 7, 8, 15, 19 Coolant pump failure 1, 2,3, 24, 27, 30 Coolant hose failure 1, 2, 3, 27, 30 Starter failure 1, 2,7, 8, 9, 12, 15 Dirty air filter 2, 3, 6, 11, 12, 17, 22

Several interesting facts can be deduced from a review of the abovelist. First, all of the failure modes listed can be at least partiallysensed by multiple sensors. In many cases, some of the sensors merelyadd information to aid in the interpretation of signals received fromother sensors. In today's automobile, there are few if any cases wheremultiple sensors are used to diagnose or predict a problem. In fact,there is virtually no failure prediction undertaken at all. Second, manyof the failure modes listed require information from more than onesensor. Third, information for many of the failure modes listed cannotbe obtained by observing one data point in time as is now done by mostvehicle sensors. Usually, an analysis of the variation in a parameter asa function of time is necessary. In fact, the association of data withtime to create a temporal pattern for use in diagnosing componentfailures in automobile is believed to be unique to this invention as isthe combination of several such temporal patterns. Fourth, the vibrationmeasuring capability of the airbag crash sensor, or other accelerometer,is useful for most of the cases discussed above yet, at the time of thisinvention, there was no such use of accelerometers except as non-crushzone mounted crash sensors. The airbag crash sensor is used only todetect crashes of the vehicle. Fifth, the second most-used sensor in theabove list, a microphone, does not currently appear on any automobilesyet sound is the signal most often used by vehicle operators andmechanics to diagnose vehicle problems. Another sensor that is listedabove which also did not currently appear on automobiles at the time ofthis invention is a pollution sensor. This is typically a chemicalsensor mounted in the exhaust system for detecting emissions from thevehicle. It is expected that this and other chemical sensors will beused more in the future.

In addition, from the foregoing depiction of different sensors whichreceive signals from a plurality of components, it is possible for asingle sensor to receive and output signals from a plurality ofcomponents which are then analyzed by the processor to determine if anyone of the components for which the received signals were obtained bythat sensor is operating in an abnormal state. Likewise, it is alsopossible to provide for a multiplicity of sensors each receiving adifferent signal related to a specific component which are then analyzedby the processor to determine if that component is operating in anabnormal state. Note that neural networks can simultaneously analyzedata from multiple sensors of the same type or different types.

The discussion above has centered on notifying the vehicle operator of apending problem with a vehicle component. Today, there is greatcompetition in the automobile marketplace and the manufacturers anddealers who are most responsive to customers are likely to benefit byincreased sales both from repeat purchasers and new customers. Thediagnostic module disclosed herein benefits the dealer by making himinstantly aware, through the cellular telephone system, or othercommunication link, coupled to the diagnostic module or system inaccordance with the invention, when a component is likely to fail.

As envisioned, on some automobiles, when the diagnostic module 266detects a potential failure, it not only notifies the driver through adisplay 278, but also automatically notifies the dealer through avehicle cellular phone 279. The dealer can thus contact the vehicleowner and schedule an appointment to undertake the necessary repair ateach party's mutual convenience. The customer is pleased since apotential vehicle breakdown has been avoided and the dealer is pleasedsince he is likely to perform the repair work. The vehicle manufactureralso benefits by early and accurate statistics on the failure rate ofvehicle components. This early warning system can reduce the cost of apotential recall for components having design defects. It could evenhave saved lives if such a system had been in place during the Firestonetire failure problem mentioned above. The vehicle manufacturer will thusbe guided toward producing higher quality vehicles thus improving hiscompetitiveness. Finally, experience with this system will actually leadto a reduction in the number of sensors on the vehicle since only thosesensors that are successful in predicting failures will be necessary.

For most cases, it is sufficient to notify a driver that a component isabout to fail through a warning display. In some critical cases, actionbeyond warning the driver may be required. If, for example, thediagnostic module detected that the alternator was beginning to fail, inaddition to warning the driver of this eventuality, the module couldsend a signal to another vehicle system to turn off all non-essentialdevices which use electricity thereby conserving electrical energy andmaximizing the time and distance that the vehicle can travel beforeexhausting the energy in the battery. Additionally, this system can becoupled to a system such as ONSTAR® or a vehicle route guidance system,and the driver can be guided to the nearest open repair facility or afacility of his or her choice.

In the discussion above, the diagnostic module of this invention assumesthat a vehicle data bus exists which is used by all of the relevantsensors on the vehicle. Most vehicles manufactured at the time of thisinvention did not have a data bus although it was widely believed thatmost vehicles will have one in the near future. A vehicle safety bus hasbeen considered for several vehicle models. Relevant signals can betransmitted to the diagnostic module through a variety of couplingsystems other than through a data bus and this invention is not limitedto vehicles having a data bus. For example, the data can be sentwirelessly to the diagnostic module using the Bluetooth or WiFispecification. In some cases, even the sensors do not have to be wiredand can obtain their power via RF from the interrogator as is well knownin the RFID (radio frequency identification) field. Alternately, aninductive or capacitive power transfer system can be used.

As can be appreciated from the above discussion, the invention describedherein brings several new improvements to automobiles including, but notlimited to, use of pattern recognition technologies to diagnosepotential vehicle component failures, use of trainable systems therebyeliminating the need of complex and extensive programming, simultaneoususe of multiple sensors to monitor a particular component, use of asingle sensor to monitor the operation of many vehicle components,monitoring of vehicle components which have no dedicated sensors, andnotification to the driver and possibly an outside entity of a potentialcomponent failure in time so that the failure can be averted and vehiclebreakdowns substantially eliminated. Additionally, improvements to thevehicle stability, crash avoidance, crash anticipation and occupantprotection are available.

To implement a component diagnostic system for diagnosing the componentutilizing a plurality of sensors not directly associated with thecomponent, i.e., independent of the component, a series of tests areconducted. For each test, the signals received from the sensors areinput into a pattern recognition training algorithm with an indicationof whether the component is operating normally or abnormally (thecomponent being intentionally altered to provide for abnormaloperation). Data from the test is used to generate the patternrecognition algorithm, e.g., a neural network, so that in use, the datafrom the sensors is input into the algorithm and the algorithm providesan indication of abnormal or normal operation of the component. Also, toprovide a more versatile diagnostic module for use in conjunction withdiagnosing abnormal operation of multiple components, tests may beconducted in which each component is operated abnormally while the othercomponents are operating normally, as well as tests in which two or morecomponents are operating abnormally. In this manner, the diagnosticmodule may be able to determine based on one set of signals from thesensors during use that either a single component or multiple componentsare operating abnormally. Of course, crash tests are also run to permitcrash sensing.

Furthermore, the pattern recognition algorithm may be trained based onpatterns within the signals from the sensors. Thus, by means of a singlesensor, it would be possible to determine whether one or more componentsare operating abnormally. To obtain such a pattern recognitionalgorithm, tests are conducted using a single sensor, such as amicrophone, and causing abnormal operation of one or more components,each component operating abnormally while the other components operatenormally and multiple components operating abnormally. In this manner,in use, the pattern recognition algorithm may analyze a signal from asingle sensor and determine abnormal operation of one or morecomponents. In some cases, simulations can be used to analyticallygenerate the relevant data.

The invention is also particularly useful in light of the foreseeableimplementation of smart highways. Smart highways will result in vehiclestraveling down highways under partial or complete control of anautomatic system, i.e., not being controlled by the driver. The on-boarddiagnostic system will thus be able to determine failure of a componentprior to and/or upon failure thereof and inform the vehicle's guidancesystem to cause the vehicle to move out of the stream of traffic, i.e.,onto a shoulder of the highway, in a safe and orderly manner. Moreover,the diagnostic system may be controlled or programmed to preventmovement of the disabled vehicle back into the stream of traffic untilrepair of the component is satisfactorily completed.

In a method in accordance with this embodiment, the operation of thecomponent would be monitored and if abnormal operation of the componentis detected, e.g., by any of the methods and apparatus disclosed herein(although other component failure systems may of course be used in thisimplementation), the vehicle guidance system which controls the movementof the vehicle would be notified, e.g., via a signal from the diagnosticmodule to the guidance system, and the guidance system would beprogrammed to move the vehicle out of the stream of traffic, or off ofthe restricted roadway, possibly to a service station or dealer, uponreception of the particular signal from the diagnostic module. Theautomatic guidance systems for vehicles traveling on highways may be anyexisting system or system being developed, such as one based onsatellite positioning techniques or ground-based positioning techniques.Since the guidance system may be programmed to ascertain the vehicle'sposition on the highway, it can determine the vehicle's currentposition, the nearest location out of the stream of traffic, or off ofthe restricted roadway, such as an appropriate shoulder or exit to whichthe vehicle may be moved, and the path of movement of the vehicle fromthe current position to the location out of the stream of traffic, oroff of the restricted roadway. The vehicle may thus be moved along thispath under the control of the automatic guidance system. In thealternative, the path may be displayed to a driver and the driver canfollow the path, i.e., manually control the vehicle. The diagnosticmodule and/or guidance system may be designed to prevent re-entry of thevehicle into the stream of traffic, or off of the restricted roadway,until the abnormal operation of the component is satisfactorilyaddressed.

FIG. 32 is a flow chart of a method for directing a vehicle off of aroadway if a component is operating abnormally. The component'soperation is monitored at 40 and a determination is made at 42 whetherits operation is abnormal. If not, the operation of the component ismonitored further (at periodic intervals). If the operation of thecomponent is abnormal, the vehicle can be directed off the roadway at44. More particularly, this can be accomplished by generating a signalindicating the abnormal operation of the component at 46, directing thissignal to a guidance system in the vehicle at 48 that guides movement ofthe vehicle off of the roadway at 50. Also, if the component isoperating abnormally, the current position of the vehicle and thelocation of a site off of the roadway can be determined at 52, e.g.,using satellite-based or ground-based location determining techniques, apath from the current location to the off-roadway location determined at54 and then the vehicle directed along this path at 56. Periodically, adetermination is made at 58 whether the component's abnormality has beensatisfactorily addressed and/or corrected and if so, the vehicle canre-enter the roadway and operation and monitoring of the component beginagain. If not, the re-entry of the vehicle onto the roadway is preventedat 60.

FIG. 33 schematically shows basic components for performing this method,i.e., a component operation monitoring system 62 (such as describedabove), an optional satellite-based or ground-based positioning system64 and a vehicle guidance system 66.

FIG. 34 illustrates the placement of a variety of sensors, primarilyaccelerometers and/or gyroscopes, which can be used to diagnose thestate of the vehicle itself. Sensor 300 can measure the acceleration ofthe firewall or instrument panel and is located thereon generally midwaybetween the two sides of the vehicle. Sensor 301 can be located in theheadliner or attached to the vehicle roof above the side door.Typically, there will be two such sensors, one on either side of thevehicle. Sensor 302 is shown in a typical mounting location midwaybetween the sides of the vehicle attached to or near the vehicle roofabove the rear window. Sensor 305 is shown in a typical mountinglocation in the vehicle trunk adjacent the rear of the vehicle. One, twoor three such sensors can be used depending on the application. If threesuch sensors are used, one would be adjacent each side of vehicle andone in the center. Sensor 303 is shown in a typical mounting location inthe vehicle door and sensor 304 is shown in a typical mounting locationon the sill or floor below the door. Finally, sensor 306, which can bealso multiple sensors, is shown in a typical mounting location forwardin a forward crush zone of the vehicle. If three such sensors are used,one would be adjacent each vehicle side and one in the center.

In general, sensors 300-306 provide a measurement of the state of thesensor, such as its velocity, acceleration, angular orientation ortemperature, or a state of the location at which the sensor is mounted.Thus, measurements related to the state of the sensor 300-306 wouldinclude measurements of the acceleration of the sensor, measurements ofthe temperature of the mounting location as well as changes in the stateof the sensor and rates of changes of the state of the sensor. As such,any described use or function of the sensors 300-306 above is merelyexemplary and is not intended to limit the form of the sensor or itsfunction.

Each of the sensors 300-306 may be single axis, double axis or triaxialaccelerometers and/or gyroscopes typically of the MEMS type. MEMS standsfor microelectromechanical system and is a term known to those skilledin the art. These sensors 300-306 can either be wired to the centralcontrol module or processor directly wherein they would receive powerand transmit information, or they could be connected onto the vehiclebus or, in some cases, using RFID technology, the sensors can bewireless and would receive their power through RF from one or moreinterrogators located in the vehicle. RFID stands for radio frequencyidentification wherein sensors are each provided with an identificationcode and designed to be powered by the energy in a radio frequency wavecontaining that code which is emitted by the interrogator. In this case,the interrogators can be connected either to the vehicle bus or directlyto control module. Alternately, an inductive or capacitive power andinformation transfer system can be used.

One particular implementation will now be described. In this case, eachof the sensors 300-306 is a single or dual axis accelerometer. They aremade using silicon micromachined technology such as disclosed in U.S.Pat. Nos. 5,121,180 and 5,894,090. These are only representative patentsof these devices and there exist more than 100 other relevant U.S.patents describing this technology. Commercially available MEMSgyroscopes such as from Systron Doner have accuracies of approximatelyone degree per second. In contrast, optical gyroscopes typically haveaccuracies of approximately one degree per hour. Unfortunately, theoptical gyroscopes are prohibitively expensive for automotiveapplications. On the other hand, typical MEMS gyroscopes are notsufficiently accurate for many control applications.

Referring now to FIG. 35, one solution is to use an IMU 311 that cancontain up to three accelerometers and three gyroscopes all produced asMEMS devices. If the devices are assembled into a single unit andcarefully calibrated to remove all predictable errors, and then coupledwith a GPS 312 and/or DGPS system 314 using a Kalman filter embodied ina processor or other control unit 313, the IMU 311 can be made to haveaccuracies comparable with military grade IMU containing precisionaccelerometers and fiber optic gyroscopes at a small fraction of thecost of the military IMU.

Thus, in connection with the control of parts of the vehicle, locationinformation may be obtained from the GPS receiver 312 and input to apattern recognition system for consideration when determining a controlsignal for the part of the vehicle. Position information from the IMU311 could alternatively or additionally be provided to the patternrecognition system. The location determination by the GPS receiver 312and IMU 311 may be improved using the Kalman filter embodied inprocessor 313 in conjunction with the pattern recognition system todiagnose, for example, the state of the vehicle.

Another way to use the IMU 311, GPS receiver 312 and Kalman filterembodied in processor 313 would be to use the GPS receiver 312 andKalman filter in processor 313 to periodically calibrate the location ofthe vehicle as determined by the IMU 311 using data from the GPSreceiver 312 and the Kalman filter embodied in processor 313. A DGPSreceiver 314 could also be coupled to the processor 313 in which case,the processor 313 would receive information from the DGPS receiver 314and correct the determination of the location of the vehicle asdetermined by the GPS receiver 312 or the IMU 311.

The angular rate function can be obtained through placing accelerometersat two separated, non-co-located points in a vehicle and using thedifferential acceleration to obtain an indication of angular motion andangular acceleration. From the variety of accelerometers shown on FIG.34, it can be readily appreciated that not only will all accelerationsof key parts of the vehicle be determined, but the pitch, yaw and rollangular rates can also be determined based on the accuracy of theaccelerometers. By this method, low cost systems can be developed which,although not as accurate as the optical gyroscopes, are considerablymore accurate than conventional MEMS gyroscopes. The pitch, yaw and rollof a vehicle can also be accurately determined using GPS and threeantennas by comparing the phase of the carrier frequency from asatellite.

Instead of using two accelerometers at separate locations on thevehicle, a single conformal MEMS-IDT gyroscope may be used. A MEMS-IDTgyroscope is a microelectromechanical system-interdigital transducergyroscope. Such a conformal MEMS-IDT gyroscope is described in a paperby V. K. Varadan, Conformal MEMS-IDT Gyroscopes and Their ComparisonWith Fiber Optic Gyro, incorporated in its entirety herein. The MEMS-IDTgyroscope is based on the principle of surface acoustic wave (SAW)standing waves on a piezoelectric substrate. A surface acoustic waveresonator is used to create standing waves inside a cavity and theparticles at the anti-nodes of the standing waves experience largeamplitude of vibrations, which serves as the reference vibrating motionfor the gyroscope. Arrays of metallic dots are positioned at theanti-node locations so that the effect of Coriolis force due to rotationwill acoustically amplify the magnitude of the waves. Unlike other MEMSgyroscopes, the MEMS-IDT gyroscope has a planar configuration with nosuspended resonating mechanical structures.

The system of FIG. 34 preferably uses dual axis accelerometers, andtherefore provides a complete diagnostic system of the vehicle itselfand its dynamic motion. Such a system is believed to be far moreaccurate than any system currently available in the automotive market.This system provides very accurate crash discrimination since the exactlocation of the crash can be determined and, coupled with knowledge ofthe force deflection characteristics of the vehicle at the accidentimpact site, an accurate determination of the crash severity and thusthe need for occupant restraint deployment can be made. Similarly, thetendency of a vehicle to roll-over can be predicted in advance andsignals sent to the vehicle steering, braking and throttle systems toattempt to ameliorate the rollover situation or prevent it. In the eventthat it cannot be prevented, the deployment side curtain airbags can beinitiated in a timely manner.

Similarly, the tendency of the vehicle to slide or skid can beconsiderably more accurately determined and again the steering, brakingand throttle systems commanded to minimize the unstable vehiclebehavior.

Thus, through the sample deployment of inexpensive accelerometers at avariety of locations in the vehicle, significant improvements are manyin the areas of vehicle stability control, crash sensing, rolloversensing, and resulting occupant protection technologies.

Finally, as mentioned above, the combination of the outputs from theseaccelerometer sensors and the output of strain gage weight sensors in avehicle seat, or in/on a support structure of the seat, can be used tomake an accurate assessment of the occupancy of the seat anddifferentiate between animate and inanimate occupants as well asdetermining where in the seat the occupants are sitting. This can bedone by observing the acceleration signals from the sensors of FIG. 34and simultaneously the dynamic strain gage measurements from seatmounted strain gages. The accelerometers provide the input function tothe seat and the strain gages measure the reaction of the occupying itemto the vehicle acceleration and thereby provide a method for dynamicallydetermining the mass of the occupying item and its location. This isparticularly important for occupant position sensing during a crashevent. By combining the outputs of accelerometers and strain gages andappropriately processing the same, the mass and weight of an objectoccupying the seat can be determined as well as the gross motion of suchan object so that an assessment can be made as to whether the object isa life form such as a human being.

For this embodiment, sensor 307 in FIG. 34 (not shown) represents one ormore strain gage or bladder weight sensors mounted on the seat or inconnection with the seat or its support structure. Suitable mountinglocations and forms of weight sensors are discussed in U.S. Pat. Nos.6,242,701 and 6,442,504 and contemplated for use in this invention aswell. The mass or weight of the occupying item of the seat can thus bemeasured based on the dynamic measurement of the strain gages withoptional consideration of the measurements of accelerometers on thevehicle, which are represented by any of sensors 300-307.

Thus, discussed above is an embodiment of a component diagnostic systemfor diagnosing the component in accordance with the invention whichcomprises a plurality of sensors not directly associated with thecomponent, i.e., independent therefrom, such that the component does notdirectly affect the sensors, each sensor detecting a signal containinginformation as to whether the component is operating normally orabnormally and outputting a corresponding electrical signal, a processorcoupled to the sensors for receiving and processing the electricalsignals and for determining if the component is operating abnormallybased on the electrical signals, and an output system coupled to theprocessor for affecting another system within the vehicle if thecomponent is operating abnormally. The processor preferably comprise apattern recognition system such as a trained pattern recognitionalgorithm such as a neural network, modular neural network or anensemble of neural networks, cellular neural networks, support vectormachines or the like. In some cases, fuzzy logic will be used which canbe combined with a neural network to form a neural fuzzy algorithm.

The second system may be a display for indicating the abnormal state ofoperation of the component arranged in a position in the vehicle toenable a driver of the vehicle to view the display and thus theindicated abnormal operation of the component. At least one source ofadditional information, e.g., the time and date, may be provided and aninput system coupled to the vehicle for inputting the additionalinformation into the processor. The second system may also be a warningdevice including a transmission system for transmitting informationrelated to the component abnormal operating state to a site remote fromthe vehicle, e.g., a vehicle repair facility.

In another embodiment of the component diagnostic system discussedabove, at least one sensor detects a signal containing information as towhether the component is operating normally or abnormally and outputs acorresponding electrical signal. A processor is coupled to the sensor(s)for receiving and processing the electrical signal(s) and fordetermining if the component is operating abnormally based hereon. Theprocessor preferably comprises a pattern recognition algorithm foranalyzing a pattern within the signal detected by each sensor. An outputsystem is coupled to the processor for affecting another system withinthe vehicle if the component is operating abnormally. The second systemmay be a display as mentioned above or a warning device.

A method for automatically monitoring one or more components of avehicle during operation of the vehicle on a roadway entails, asdiscussed above, monitoring operation of the component in order todetect abnormal operation of the component, e.g., in one or the waysdescribed above, and if abnormal operation of the component is detected,automatically directing the vehicle off of the restricted roadway. Forexample, in order to automatically direct the vehicle off of therestricted roadway, a signal representative of the abnormal operation ofthe component may be generated and directed to a guidance system of thevehicle that guides the movement of the vehicle. Possibly the directingthe vehicle off of the restricted roadway may entail applying satellitepositioning techniques or ground-based positioning techniques to enablethe current position of the vehicle to be determined and a location offof the restricted highway to be determined and thus a path for themovement of the vehicle. Re-entry of the vehicle onto the restrictedroadway may be prevented until the abnormal operation of the componentis satisfactorily addressed.

The state of the entire vehicle may be diagnosed whereby two or moresensors, preferably acceleration sensors and gyroscopes, detect thestate of the vehicle and if the state is abnormal, an output system iscoupled to the processor for affecting another system in the vehicle.The second system may be the steering control system, the brake system,the accelerator or the frontal or side occupant protection system.

An exemplifying control system for controlling a part of the vehicle inaccordance with the invention thus comprises a plurality of sensors orsystems mounted at different locations on the vehicle, each sensorsystem providing a measurement related to a state of the sensor systemor a measurement related to a state of the mounting location, and aprocessor coupled to the sensors or sensor systems and arranged todiagnose the state of the vehicle based on the measurements of thesensor system, e.g., by the application of a pattern recognitiontechnique. The processor controls the part based at least in part on thediagnosed state of the vehicle.

At least one of the sensors or sensor systems may be a high dynamicrange accelerometer or a sensor selected from a group consisting of asingle axis acceleration sensor, a double axis acceleration sensor, atriaxial acceleration sensor and a gyroscope, and may optionally includean RFID (radio frequency identification) response unit. The gyroscopemay be a MEMS-IDT (microelectromechanical system-interdigitaltransducer) gyroscope including a surface acoustic wave resonator whichapplies standing waves on a piezoelectric substrate. If an RFID responseunit is present, the control system would then comprise an RFIDinterrogator device which causes the RFID response unit(s) to transmit asignal representative of the measurement of the sensor system associatedtherewith to the processor.

The state of the vehicle diagnosed by the processor may be the vehicle'sangular motion, angular acceleration and/or angular velocity. As such,the steering system, braking system or throttle system may be controlledby the processor in order to maintain the stability of the vehicle. Theprocessor can also be arranged to control an occupant restraint orprotection device in an attempt to minimize injury to an occupant.

The state of the vehicle diagnosed by the processor may also be adetermination of a location of an impact between the vehicle and anotherobject. In this case, the processor can forecast the severity of theimpact using the force/crush properties of the vehicle at the impactlocation and control an occupant restraint or protection device based atleast in part on the severity of the impact.

The system can also include a weight sensing system coupled to a seat inthe vehicle for sensing the weight of an occupying item of the seat. Theweight sensing system is coupled to the processor whereby the processorcontrols deployment or actuation of the occupant restraint or protectiondevice based on the state of the vehicle and the weight of the occupyingitem of the seat sensed by the weight sensing system.

A display may be coupled to the processor for displaying an indicationof the state of the vehicle as diagnosed by the processor. A warningdevice may be coupled to the processor for relaying a warning to anoccupant of the vehicle relating to the state of the vehicle asdiagnosed by the processor. Further, a transmission device may becoupled to the processor for transmitting a signal to a remote siterelating to the state of the vehicle as diagnosed by the processor.

The state of the vehicle diagnosed by the processor may include angularacceleration of the vehicle whereby angular velocity and angularposition or orientation are derivable from the angular acceleration. Theprocessor can then be arranged to control the vehicle's navigationsystem based on the angular acceleration of the vehicle.

A method for controlling a part of the vehicle in accordance with theinvention comprises mounting a plurality of sensors or sensor systems atdifferent locations on the vehicle, measuring a state of the sensorsystem or a state of the respective mounting location of the sensorsystem, diagnosing the state of the vehicle based on the measurements ofthe state of the sensors or sensor systems or the state of the mountinglocations of the sensors or sensor systems, and controlling the partbased at least in part on the diagnosed state of the vehicle. The stateof the sensor system may be any one or more of the acceleration, angularacceleration, angular velocity or angular orientation of the sensorsystem. Diagnosis of the state of the vehicle may entail determiningwhether the vehicle is stable or is about to rollover or skid and/ordetermining a location of an impact between the vehicle and anotherobject. Diagnosis of the state of the vehicle may also entaildetermining angular acceleration of the vehicle based on theacceleration measured by accelerometers if multiple accelerometers arepresent as the sensors or sensor systems.

Another control system for controlling a part of the vehicle inaccordance with the invention comprises a plurality of sensors or sensorsystems mounted on the vehicle, each providing a measurement of a stateof the sensor system or a state of the mounting location of the sensorsystem and generating a signal representative of the measurement, and apattern recognition system for receiving the signals from the sensors orsensor systems and diagnosing the state of the vehicle based on themeasurements of the sensors or sensor systems. The pattern recognitionsystem generates a control signal for controlling the part based atleast in part on the diagnosed state of the vehicle. The patternrecognition system may comprise one or more neural networks. Thefeatures of the control system described above may also be incorporatedinto this control system to the extent feasible.

The state of the vehicle diagnosed by the pattern recognition system mayinclude a state of an abnormally operating component whereby the patternrecognition system is designed to identify a potentially malfunctioningcomponent based on the state of the component measured by the sensors orsensor systems and determine whether the identified component isoperating abnormally based on the state of the component measured by thesensors or sensor systems.

In one preferred embodiment, the pattern recognition system may comprisea neural network system and the state of the vehicle diagnosed by theneural network system includes a state of an abnormally operatingcomponent. The neural network system includes a first neural network foridentifying a potentially malfunctioning component based on the state ofthe component measured by the sensors or sensor systems and a secondneural network for determining whether the identified component isoperating abnormally based on the state of the component measured by thesensors or sensor systems.

Modular neural networks can also be used whereby the neural networksystem includes a first neural network arranged to identify apotentially malfunctioning component based on the state of the componentmeasured by the sensors or sensor systems and a plurality of additionalneural networks. Each of the additional neural networks is trained todetermine whether a specific component is operating abnormally so thatthe measurements of the state of the component from the sensors orsensor systems are input into that one of the additional neural networkstrained on a component which is substantially identical to theidentified component.

Another method for controlling a part of the vehicle comprises mountinga plurality of sensors or sensor systems on the vehicle, measuring astate of the sensor system or a state of the respective mountinglocation of the sensor system, generating signals representative of themeasurements of the sensors or sensor systems, inputting the signalsinto a pattern recognition system to obtain a diagnosis of the state ofthe vehicle and controlling the part based at least in part on thediagnosis of the state of the vehicle.

In one notable embodiment, a potentially malfunctioning component isidentified by the pattern recognition system based on the statesmeasured by the sensors or sensor systems and the pattern recognitionsystem determine whether the identified component is operatingabnormally based on the states measured by the sensors or sensorsystems. If the pattern recognition system comprises a neural networksystem, identification of the component entails inputting the statesmeasured by the sensors or sensor systems into a first neural network ofthe neural network system and the determination of whether theidentified component is operating abnormally entails inputting thestates measured by the sensors or sensor systems into a second neuralnetwork of the neural network system. A modular neural network systemcan also be applied in which the states measured by the sensors orSensor systems are input into a first neural network and a plurality ofadditional neural networks are provided, each being trained to determinewhether a specific component is operating abnormally, whereby the statesmeasured by the sensors or sensor systems are input into that one of theadditional neural networks trained on a component which is substantiallyidentical to the identified component.

Another control system for controlling a part of the vehicle based onoccupancy of the seat in accordance with the invention comprises aplurality of strain gages mounted in connection with the seat, eachmeasuring strain of a respective mounting location caused by occupancyof the seat, and a processor coupled to the strain gages and arranged todetermine the weight of an occupying item based on the strainmeasurements from the strain gages over a period of time, i.e., dynamicmeasurements. The processor controls the part based at least in part onthe determined weight of the occupying item of the seat. The processorcan also determine motion of the occupying item of the seat based on thestrain measurements from the strain gages over the period of time. Oneor more accelerometers may be mounted on the vehicle for measuringacceleration in which case, the processor may control the part based atleast in part on the determined weight of the occupying item of the seatand the acceleration measured by the accelerometer(s).

By comparing the output of various sensors in the vehicle, it ispossible to determine activities that are affecting parts of the vehiclewhile not affecting other parts. For example, by monitoring the verticalaccelerations of various parts of the vehicle and comparing theseaccelerations with the output of strain gage load cells placed on theseat support structure, a characterization can be made of the occupancyof the seat. Not only can the weight of an object occupying the seat bedetermined, but also the gross motion of such an object can beascertained and thereby an assessment can be made as to whether theobject is a life form such as a human being. Strain gage weight sensorsare disclosed in U.S. Pat. No. 6,242,701. In particular, the inventorscontemplate the combination of all of the ideas expressed in this patentwith those expressed in the current invention.

4.5 Smart Airbags

A block diagram of the neural network computer method of obtaining asmart airbag algorithm is illustrated in FIG. 36. In the first step, oneor more vehicle models are crashed under controlled conditions where thevehicle and crash dummies are fully instrumented so that the severity ofthe crash, and thus the need for an airbag, can be determined. Anoccupant sensor is also present and in use so that key occupant motiondata can be obtained. The occupant data will be insufficient for thefull neural network algorithm development but will provide importantverification data. Acceleration during the crash is measured at allpotential locations for mounting the crash sensors. Normally, anyposition which is rigidly attached to the main structural members of thevehicle is a good mounting location for the non-crush zone sensors.

The following crash event types, at various velocities, arerepresentative of those that should be considered in establishing crashsensor designs and calibrations for frontal impacts, a similar set alsoexists for side and rear impacts:

-   -   Frontal Barrier Impact    -   Right Angle Barrier Impact    -   Left Angle Barrier Impact    -   Frontal Offset Barrier Impact    -   Frontal Far Offset (Outside of Rails) Barrier Impact    -   High Pole on Center Impact    -   High Pole off Center Impact    -   Low Pole (below bumper) Impact    -   Frontal Car-to-Car Impact    -   Partial Frontal Car-to-Car Impact    -   Angle car-to-car Impact    -   Front to Rear car-to-car Impact    -   Front to Side Car-to-Car Impact, Both Cars Moving    -   Bumper Underride Impact    -   Animal Impact—Simulated Deer    -   Undercarriage Impact (hang-up on railroad track type of object)    -   Impact Into Highway Energy Absorbing Device (Yellow Barrels,        etc.)    -   Impact Into Guardrail    -   Curb Impacts

The following non-crash event types are representative of thoseconsidered in establishing crash sensor designs and calibrations:

-   -   Hammer Abuse (shop abuse)    -   Rough Road (rough driving conditions)

Normally, a vehicle manufacturer will only be concerned with aparticular vehicle model and instruct the crash sensor designer todesign a sensor system for that particular vehicle model. This is ingeneral not necessary when using the techniques described herein andvehicle crash data from a variety of different vehicle models can beincluded in the training data.

Since the system is typically being designed for a particular vehiclemodel, static occupant data needs to be obtained for that particularmodel and still maintain approximately 100% accuracy. As vision systemsimprove, the ability to move systems from vehicle to vehicle will alsoimprove and eventually all of the occupant portion of the training willbe done by simulation and through use of databases on a computer.Although crash data from one vehicle can frequently be used for thetraining purposes, occupant data cannot in general be interchanged fromone vehicle model to another vehicle model. Dynamic position data for anoccupant will, in general, be analytically derived based on the initialposition and rules as to how the body translates and rotates which willbe determined from sled and crash tests. This is not as complicated asmight first appear since for most practical purposes, an unbeltedoccupant will just translate forward as a free mass and thus the initialposition plus the acceleration of the vehicle allows a reasonablyaccurate determination of position over time. The problem is morecomplicated for a belted occupant and rules governing occupant motionmust be learned from modeling and verified by sled and crash tests.Fortunately, belted occupants are unlikely to move significantly duringthe critical part of the crash and thus, the initial position plus somebelt payout and stretch at least for the chest is a good approximation.

The vehicle manufacturer will be loath to conduct all of the crasheslisted above for a particular vehicle since crash tests are veryexpensive. If, on the other hand, a particular crash type that occurs inthe real world is omitted from the library, there is a chance that thesystem will not perform optimally when the event occurs later and one ormore people will unfortunately be killed or injured. One way topartially solve this dilemma is to use crash data from other vehicles asdiscussed above. Another method is to create data using the dataobtained from the staged crash tests and operating on the data usingvarious mathematical techniques that permits the creation of data thatis representative of crashes not run. One method of accomplishing thisis to use velocity and crash scaling as described in detail in the abovereferenced papers and particularly in reference (1) at page 8 andreference (2) at pages 3749. This is the second step in the processillustrated in FIG. 36. Also included in the second step is theanalytical determination of the occupant motion discussed above.

The third step is to assume a candidate neural network architecture. Achoice that is moderately complex is suggested such as one with 100input nodes and 6 hidden layer nodes. If the network is too simple,there will be cases for which the system cannot be trained and, if theseare important crashes, the network will have to be revised by addingmore nodes. If the initial choice is too complex, this will usually showup after the training with one or more of the weights having a near zerovalue. In any event, the network can be tested later by removing onenode at a time to see if the accuracy of the network degrades.Alternately, genetic algorithms are used to search for the optimumnetwork architecture. A similar set of steps apply to other patternrecognition technologies.

Usually a combination neural network is used and tools are now availableof generating and training such a network. This is described in somedetail for occupant sensing in U.S. Pat. No. 6,445,988.

The training data must now be organized in a fashion similar to the wayit will be seen on a vehicle during a crash. Although data from apreviously staged crash is available for the full time period of thecrash, the vehicle-mounted system will only see the data one value at atime. Thus, the training data must be fed to the pattern recognitioncomputer, or computer program, in that manner. This can be accomplishedby taking each crash data file and creating 100 cases from it, assumingthat the time period chosen for a crash is 200 milliseconds and thateach data point is the pre-processed acceleration over two milliseconds.This data must also be combined with the occupant data derived asdiscussed above. The first training case contains the first crash datapoint and the remaining 99 points are zero, or random small values forthe crash data nodes, and the segmented occupant position data asdescribed in U.S. RE37260 for the occupant nodes.

Since the handling of the occupant data is described in the '260 patent,the remaining description here will be limited to the handling of thecrash data. The second crash data case contains the first two datapoints with the remaining 98 points set to zero or random low valuesetc. For the tenth data file, data point one will contain the 2 msaverage acceleration at twenty milliseconds into the crash, data pointtwo the average acceleration at eighteen milliseconds into the crash,and data point ten will contain the data from the first two millisecondsof the crash. This process is continued until the one hundred data casesare created for the crash. Each case is represented as a line of data inthe training file. This same process must be done for each of thecrashes and non-crash events for which there is data. A typical trainingset will finally contain on the order of 50,000 crash data cases and500,000 occupant static data cases. The addition of other data such asfrom multiple accelerometers and gyroscopes can result in a significantincrease in the dataset. One variable that has not been considered ispre-crash braking. This can influence the initial crash data pointsprior to the start of the crash, those that were set to small randomvalues. One alternative to eliminate this influence, since pre-crashbraking may or may not be present, is to set all acceleration valuesless than 1 G to zero. On the other hand, there can be significantinformation in the pre-crash braking data and therefore it may bedesirable to present this as additional information for the smart airbagsystem to consider.

In the pure neural network crash sensor case as described in U.S. Pat.No. 5,684,701, it was possible to substantially trim the data set toexclude all those cases for which there is no definite requirement todeploy the restraint and the same is true here. For a particular 30 mphfrontal barrier crash, for example, analysis of the crash has determinedthat the sensor must trigger the deployment of the airbag by 20milliseconds for a 50% male with the seat in the mid seating position.For data greater than 20 milliseconds, the data is of little value fromthe point of view of a neural network crash sensor that only needs todetermine whether to deploy the airbag since that would represent a latedeployment, such is not the case here since, for some gas controlmodules, the inflation/deflation rate can be controlled after thedecision to deploy. Also, the 20 millisecond triggering requirement isno longer applicable since it depends on the initial seating positionand perhaps the size of the occupant.

For cases where the airbag should not trigger, on the other hand, theentire data set of 200 data files must be used. Finally, the trainingset must be balanced so that there are about as many no-trigger cases astrigger cases so that the output will not be biased toward one or theother decision. This then is the fourth step in the process as depictedin FIG. 36.

In the fifth step, the pattern recognition program is run with thetraining set. The program, if it is a neural network program, uses avariety of techniques such as the “back propagation” technique to assignweights to the connections from the input layer nodes to the hiddenlayer nodes and from the hidden layer nodes to the output layer nodes totry to minimize the error at the output nodes between the valuecalculated and the value desired. For example, for a particular crashsuch as a 30 mph frontal barrier impact, an analysis of the crash andthe particular occupant has yielded the fact that the sensor musttrigger in 20 milliseconds and the data file representing the first 20milliseconds of the crash would have a desired output node value whichwould instruct the gas module to inject a particular amount of gas intothe airbag.

For another crash such as an 8 mph barrier crash where airbag deploymentis not desired, the desired output value for all of the data vectorswhich are used to represent this crash (100 vectors) would haveassociated with them a desired output node value of 0 which correspondsto a command to the gas control module not to inject or direct gas intothe airbag. The network program then assigns different weights to thenodes until all of the airbag-deployment-not-desired cases have anoutput node value nearly equal to 0 and similarly, all of theairbag-deployment-desired cases have an output value close to that whichis required for the gas control module to inject the proper amount ofgas into the airbag. The program finds those weights that minimize theerror between the desired output values and the calculated outputvalues.

Since a neural network may have a problem with the discontinuity betweenzero gas flow and a substantial flow needed even for a marginal airbagdeployment, a continuous function may be used and then interpreted suchthat all flows below a certain value are set to zero at postprocessing.

The term weight is a general term in the art used to describe themathematical operation that is performed on each datum at each node atone layer before it is inputted into a node at a higher layer. The dataat input layer node 1, for example, will be operated on by a functionthat contains at least one factor that is determined by the trainingprocess. In general this factor, or weight, is different for eachcombination of an input node and hidden layer node. Thus, in the exampleabove where there were 100 input nodes, 12 hidden layer nodes and 1output node, there will in general be 1,212 weights which are determinedby the neural network program during the training period. An example ofa function used to operate on the data from one node before it is inputto a higher level node is the sigmoid function:

In the usual back propagation trained network, let

-   -   O_(ij) be the output of node j in layer i,

then the input to node k in layer i+l isI _(i+l,k)=Σ_(j) W _(kj) ^((i)) O _(ij)

where W_(kj) ^((i)) is the weight applied to the connection between nodej in layer i and node k in layer i+1.

Then the output of node k in layer i+1 is found by transforming itsinput, for example, with the sigmoid function:O _(i+l,k)=1/(1+e ^(−li+lk))

and this is used in the input to the next, i+2, layer.

If the neural network is sufficiently complex, that is if it has manyhidden layer nodes, and if the training set is small, the network may“memorize” the training set with the result that it can fail to respondproperly on a slightly different case from those presented. This is oneof the problems associated with neural networks which is now beingsolved by more advanced pattern recognition systems including geneticalgorithms which permits the determination of the minimum complexitynetwork to solve a particular problem. Memorizing generally occurs onlywhen the number of vectors in the training set is not sufficiently largecompared to the number of weights. The goal is to have a network thatgeneralizes from the data presented and therefore will respond properlyto a new case that is similar to but only slightly different from one ofthe cases presented.

The network can also effectively memorize the input data if many casesare nearly the same. It is sometimes difficult to determine this bylooking at the network so it is important that the network not betrained on all available data but that some significant representativesample of the data is held out of the training set to be used to testthe network. It is also important to have a training set which is verylarge (one hundred to one thousand times the number of weights or moreis desirable). This is the function of step five, to test the networkusing data that it has not seen before, i.e., which did not constitutepart of the training data.

Step six involves redesigning the network and then repeating steps threethrough five until the results are satisfactory. This step isautomatically accomplished by some of the neural network softwareproducts available on the market.

The final step is to output the computer code for the algorithm and toprogram a microprocessor, FPGA or design an ASIC with a neural computer,with this code. One important feature of this invention is that theneural network system chosen is very simple and yet, because of the waythat the data is fed to the network, all relevant calculations are madewith a single network. There is no need, for example, to use anadditional network to translate a prediction of a vehicle velocitychange, and thus the crash severity, into a time to trigger airbagdeployment or the setting for the gas controller. In fact, to do thiswould be difficult since the entire time history would need to beconsidered. The output from the network is the setting of the gascontroller in the preferred implementation. Naturally, there may becases where some intermediate step might be desirable.

The steps described above and illustrated in FIG. 36 are for the casewhere a neural computer program is used to generate code that will bethen used to program a standard microprocessor. Similar steps apply alsoto the case where a neural computer is used. Finally, smart seatbeltsare under development wherein the seatbelt induced deceleration to theoccupant is another controllable parameter and when available they canalso be incorporated in the above smart airbag development process.

5 Summary

Disclosed herein is an airbag deployment system which comprises at leastone module housing, at least one deployable airbag associated with eachhousing, an inflator associated with each housing for inflating theairbag(s) to deploy, e.g., into the passenger compartment, an airbaginflation determining system for determining that deployment of theairbag(s) is/are desired, and a respective electronic control systemarranged within or proximate each housing and coupled to a respectiveinflator and to the airbag inflation determining system for initiatingthe inflator to inflate the airbag(s) in the respective housing uponreceiving a signal from the airbag inflation determining system. Thecontrol device includes a power supply for enabling initiation of theinflator. The airbag inflation determining system preferably generates acoded signal when deployment of the airbag(s) is desired and the controldevice receive the coded signal and initiate the inflator based thereon.

The system may also comprise an occupant position sensor orposition-sensing system coupled to the control device of each housingfor detecting the position of an occupant to be protected by thedeployment of the airbag from the housing. In this case, the controldevice initiates the respective inflator to inflate the airbag(s) in therespective housing in consideration of (or based in part on) thedetected position of the occupant. Also, the position sensing system maycomprise a wave transmitter for transmitting waves into the passengercompartment and a wave receiver for receiving waves from the passengercompartment, the wave transmitter and wave receiver both being coupledto the control device. The control device may send a signal to the wavetransmitter to cause the wave transmitter to transmit the waves into thepassenger compartment. In some embodiments, there are several housingsand the system thus may include a delay unit arranged in associationwith at least one housing for providing a delay in the inflation of theairbag(s) therein initiated by the control device associated with thehousing upon receiving the signal from the airbag inflation determiningsystem. The delay device provides variable delays in the inflation ofthe airbag(s) in the housings such that the airbag(s) in the housingsinflate at different times.

The system may also include a diagnostic component arranged within eachhousing for determining the status of the control device, and amonitoring system coupled to each diagnostic component for receiving thestatus of the control device associated with each module and providing awarning if the control device of any module fails. The airbag inflationdetermining system and control device may be arranged on a singlevehicle bus.

The aspect of reducing the concentration of toxic gas in the passengercompartment resulting from airbag deployment in the present invention iscentered around solving the problem of an excess build up of pressurewhen more than two airbags (or an unconventionally large airbag) aredeployed in an accident by reducing the pressure before, during and/orafter deployment of a plurality of airbags. Initially, care is taken toreduce the problem by not deploying any unnecessary airbags by detectingthe presence of occupants on particular seats. Thus, if there is nofront seat passenger present then the airbags designed to protect suchan occupant are not inflated. This is not for the purpose of minimizingthe repair costs as is the object of other similar systems, but tocontrol the pressure buildup when multiple airbags are deployed. After adecision is made as to what seats need to be protected, the next step isto determine how many airbags are needed to provide the best protectionto the vehicle occupants in those seats. This might require thedeployment of a knee airbag, especially if the occupant is not wearing aseatbelt, and of a side head protection airbag if the frontal impact hasan angular component which might cause the occupant's head to strike theA-pillar of the vehicle, for example. When the total number of airbagsdeployed exceeds a given number, a system is then provided to open ahole in the vehicle to reduce the pressure buildup.

Other factors are taken into account to determine the particular givennumber of deploying airbags that necessitate the opening of a hole.These include the use of highly aspirated airbags systems. Aspiratedsystems are in use but not always for the purpose of reducing thepressure buildup in the vehicle caused by the deployment of multipleairbags. Indeed, it has been the case that no more than two airbags haveyet been deployed in a vehicle accident.

An unexpected result of the pressure reducing features of the presentinvention is the fact that now propellants which have heretofore notbeen considered for airbags can now be used which substantially reducethe cost and improve the performance of airbag systems.

A further unexpected result of the incorporation of the electronics intothe module feature of the present invention is that the reliability ofthe system is substantially improved.

In one embodiment disclosed herein, the airbag module in accordance withthe invention is long and thin and can conveniently be made in anylength and bent into almost any generally linear shape. This module istypically mounted on or slightly below a surface in the passengercompartment such as the ceiling, instrument panel, seat or knee bolstersupport structure. When the deployment of the module is initiated, acover is released and a thin, preferably film, airbag is inflated usinga highly aspirated inflator using a clean propellant which if undilutedmight be toxic to humans.

More particularly, in certain embodiments in accordance with theinvention, the airbag module comprises an elongate housing having alength in the longitudinal direction which is substantially larger thana width or thickness thereof in a direction transverse to thelongitudinal direction, an airbag situated within the housing, aninflator arranged in the housing for producing pressurized gas toinflate the airbag, mounting structure for mounting the module in thepassenger compartment, an initiation device for initiating the inflatorto produce the pressurized gas in response to the crash of the vehicle,and the housing comprises a cover unit for releasably retaining theairbag. Preferably, the length of the housing is at least ten timeslarger than the width or the thickness of the housing thereby permittingmounting of the module with minimal penetration below a mounting surfaceof the passenger compartment. In one embodiment, the inflator and airbagextend in the longitudinal direction of the housing and the inflator iselongate and has a length which is more than half the length of theairbag measured in the longitudinal direction when the airbag isinflated. The airbag system also optionally includes a system forreducing the concentration of toxic gas in the passenger compartmentwhich are ideally activated upon deployment of the airbag.

The inflator may comprise a gas generator having a length substantiallyin the longitudinal direction of the housing exceeding ten times a widthor thickness of the gas generator in a direction transverse to thelongitudinal direction.

Furthermore, the housing includes an elongate support base mounted to asurface of the passenger compartment by the mounting structure and whichhas a catch at each longitudinal side. In this embodiment, the coverunit comprises a tab engaging with the catch to retain the cover unit,the tab being released from the catch during deployment of the airbag.

In another embodiment disclosed herein, the inflator comprises anelongate gas generator including a propellant for producing pressurizedgas to inflate the airbag which has a length at least ten times itswidth or thickness. The module is mounted substantially onto aperipheral surface of the passenger compartment while the initiationdevice is structured and arranged to initiate the gas generator toproduce the pressurized gas in response to the crash of the vehicle. Thecover unit covers the airbag prior to the production of the pressurizedgas and the housing further includes a removal system for enablingremoval of the cover unit to permit the deployment of the airbag. Thesurface of the passenger compartment to which the module is mounted is aback surface of a front seat of the vehicle, an instrument panel in thevehicle, possibly in such a position as to afford protection to theknees of a front seat occupant during the crash of the vehicle, or theceiling of the vehicle, e.g., at a location in front of a front seat ofthe vehicle and suitable for mounting the module for protectingoccupants of the front seat in a frontal impact or at a location along aside of the vehicle and suitable for mounting the module for protectingoccupants of both front and rear seats in a side impact or at a locationbehind a front seat of the vehicle.

In yet another embodiment disclosed herein, the inflator comprises anelongate gas generator for producing the pressurized gas to inflate theairbag and therefore, the initiation system is structured and arrangedto initiate the gas generator to produce the pressurized gas in responseto the crash of the vehicle. The module further includes an aspirationsystem for combining gas from the passenger compartment with thepressurized gas from the gas generator and directing the combined gasinto the airbag. Such an aspiration system may comprise a linear nozzleleading from a combustion chamber in the gas generator and having aconverging section followed by a diverging section and ending at amixing chamber in the module, whereby the pressurized gas flows from thecombustion chamber through the linear nozzle into the mixing chamber,and defines at least one aspiration inlet port such that gas from thepassenger compartment flows through the aspiration inlet port into themixing chamber. The mixing length is at least fifty times the minimumthickness of a jet of the pressurized gas from the gas generator withinthe nozzle. The mixing chamber comprises a nozzle defining a convergingsection and a diverging section arranged after the converging section ina direction of flow of the combined pressurized gas and gas from thepassenger compartment. The dimensions of the converging-diverging nozzleand aspiration inlet port(s) are selected so that the gas entering theairbag is at least about 80 percent from the passenger compartment. Theaspiration system may also comprise a pair of nozzle walls extending inthe longitudinal direction at a respective side of the gas generator,such that the gas generator is situated between the nozzle walls and thepressurized gas from the gas generator is directed into a mixing chamberdefined in part between the nozzle walls, and springs for connecting thenozzle walls to the support base. The springs have a first position inwhich the nozzle walls are proximate to the support base and a secondposition in which the nozzle walls are spaced apart from the supportbase. The springs are extended to the second position during productionof the pressurized gas to separate the nozzle walls from the supportbase to define aspiration inlet ports between the nozzle walls and thesupport base. In this case, the module also includes support shieldsconnected to and extending between the nozzle walls. The support shieldsdefine the mixing chamber prior to deployment of the airbag and areforced outward to define a second converging-diverging nozzle leadingfrom the mixing chamber to the airbag through which the pressurized gasflows.

The gas generator preferably comprises an elongate housing, which may bemade of plastic, having a length at least 10 times its thickness orwidth, propellant dispersed in an interior of and substantially alongthe length of the gas generator housing, an igniter for initiatingburning of the propellant; and a gas generator mounting system formounting the gas generator in the passenger compartment. The gasgenerator housing comprises at least one opening through which gaspasses from the interior of the gas generator into the airbag. Theopening(s) has/have a variable size depending on the pressure of the gasin the interior of the gas generator housing.

The present invention also relates to an occupant protection system fora vehicle including an airbag module and having a power steering systemcomprising a steering wheel opposed to a driver side portion of a frontseat, a servo control system and structure for connecting the steeringwheel to the control system, e.g., a deformable support member. Themodule is mounted in the passenger compartment apart from the steeringwheel of the vehicle. In this case, the occupant protection systemcomprises a yieldable steering wheel support system for enabling thesteering wheel to be displaced away from a position opposed to a driverwhen situated in the driver side portion of the front seat. The moduleis thus structured and arranged such that the airbag after deploymentcushions the driver from impact with surfaces of the passengercompartment. As such, it is possible to provide a single airbag moduleto provide protection for the entire front seat which would deploy anairbag from one side of the vehicle to the other side.

It is also envisioned that a single airbag module can provide protectionfor both a front seat occupant and a rear seat occupant on the same sideof the vehicle. In this case, the airbag module is mounted to a surfaceof the passenger compartment such that it extends in a horizontaldirection from a front portion of the passenger compartment toward arear portion of the passenger compartment adjacent a side of thevehicle. The module would deploy an airbag extending substantiallyacross the entire side of the vehicle alongside the front seat and therear seat.

Furthermore, it will be appreciated by those skilled in the art, and asexplained below, that it is ideal to vary the size of the nozzle of thegas generator through which gas generated by the burning propellantflows in response to variations in the pressure in the chamber in whichthe propellant is burning. To this end, the present invention includes agas generator having a housing, propellant dispersed in an interiorthereof, an igniter for initiating burning of the propellant, and a gasgenerator mounting system for mounting the gas generator housing to thesupport base and spaced from the support base to define a nozzletherebetween and which comprise elastic support brackets arranged in thenozzle between the gas generator housing and the support base or stripsof deformable material, which deforms as a function of temperaturevariation, arranged in the nozzle between the gas generator housing andthe support base.

In yet another embodiment disclosed herein, the airbag module comprisesan airbag, an inflator for producing pressurized gas to inflate theairbag and which comprises a housing, a gas generator arranged therein,and a variable exit opening from the housing through which gas from thegas generator flows to inflate the airbag. The size of the variable exitopening is controlled by the pressure within the housing. The remainingstructure of this module may be as described above.

One embodiment of the vehicle electrical system in accordance with theinvention discussed above includes a plurality of electrical devicesused in the operation of the vehicle, a single communication bus, all ofthe devices being connected to the communication bus and a single powerbus, all of the devices being connected to the power bus (which may beone and the same as the communication bus). The devices are preferablyprovided with individual device addresses such that each device willrespond only to its device address. Each bus may comprise a pair ofwires connected to all of the devices. The devices are, e.g., actuators,sensors, airbag modules, seatbelt retractors, lights and switches. Ifeach device is assigned a unique address, the communication bus may bearranged to transfer data in the form of messages each having an addressof a respective device such that only the respective device assigned tothat address is responsive to the message having the address. Eachdevice thus determines whether the messages of the communication businclude the address assigned to the device, e.g., a microprocessor. Thecommunication bus may also include a token ring network to provide aprotocol for the transfer of messages through the communication bus.Each device may be arranged to acknowledge receipt of a communicationvia the communication bus and indicate operability of the device uponignition of the vehicle.

Another electrical system for a vehicle in accordance with the inventioncomprises a plurality of devices used in the operation of the vehicle,and a single network constituting both a power distribution and acommunication/information bus. The network may be a time multiplexnetwork or a code division multiple access or other shared network andconsists of a single wire, or a pair of wires, connecting all of thedevices. For the single wire case, each device is grounded to anadjacent part of the vehicle.

Still another electrical system for a vehicle in accordance with theinvention comprises a plurality of sensors, each detecting a physicalcharacteristic, property or state of the vehicle, and a data bus, all ofthe sensors being connected to the data bus. A module is also preferablyconnected to the data bus and arranged to receive signals from thesensors and process the signals to provide information derived from thephysical characteristics, properties or states detected by the sensors.The module may be arranged to process the physical characteristics,properties or states detected by the sensors to determine whether acomponent in the vehicle is operating normally or abnormally. A display,e.g., a light on the vehicle dashboard, may be coupled to the module fordisplaying the information derived from the physical characteristics,properties or states detected by the sensors. A telecommunicationsdevice may also be coupled to the module for communicating with a remotestation to provide the remote station with the information derived fromthe physical characteristics, properties or states detected by thesensors, e.g., impending failure of a specific vehicle component or avehicle crash. More specifically, the sensors may generate signalscontaining information as to whether the component is operating normallyor abnormally whereby the module comprises a pattern recognition systemfor receiving the signals and ascertaining whether the signals containpatterns representative of normal or abnormal operation of thecomponent.

With a single pair of wires in a twisted pair or coaxial configurationfor the communication bus, and perhaps another for the power bus, theconnector problem can now be addressed as a single design can be usedfor all connections on the bus and each connector will only beconnecting at most two wires. A great deal of effort can thus be appliedto substantially improve the reliability of such a connector.

In another embodiment of a vehicle electrical wiring system inaccordance with the invention, substantially all of the devices, andespecially substantially all of the safety devices, are connectedtogether with a single communication bus and a single power bus. In thepreferred case, a single wire pair will serve as both the power andcommunication buses. When completely implemented each device on thevehicle will be coupled to the power and communication buses so thatthey will now have an intelligent connection and respond only to datathat is intended for that device, that is, only that data with theproper device address.

The benefits to be derived from the vehicle electrical system describedherein include at least at 50% cost saving when fully implementedcompared with current wire harnesses. A weight savings of at least 50%is also expected. Most importantly, a multi-fold improvement inreliability will result. The assembly of the system into the vehicle isgreatly simplified as is the repair of the system in the event thatthere is a failure in the wiring harness. Most of the connectors areeliminated and the remaining ones are considerably more reliable.Diagnostics on all devices on key-on can now be accomplished over thenetwork with a single connection from the diagnostic circuit.

In contrast to other multiplexing systems based on zone modules, thecommunication to and from each device in the instant invention isbi-directional.

It is now believed that for side impacts, the airbag crash sensor shouldbe placed in the door. There is reluctance to do so by the automobilemanufacturers since in a crash into the A-pillar of the vehicle, forexample, the wires leading to and form the door may be severed beforethe crash sensor activates. By using the two wire network as describedherein, only two, or possibly four if a separate pair is used for power,of wires will pass from the door into the A-pillar instead of thetypically fifty or more wires. In this case, the wires can be protectedso that they are stronger than the vehicle metal and therefore will notsever during the early stages of the accident and thus the door mountedsensor can now communicate with the airbag in the seat, for example.

In the preferred system then, the power line or distribution network inthe vehicle is used to simultaneously carry both power and data to allswitches, sensors, lights, motors, actuators and all other electricaland electronic devices (hereinafter called devices) within the vehicleand especially all devices related to deployable restraints. The samesystem will also work for vehicles having different voltages such as 48volts. Also a subset of all vehicle devices can be on a net. Initially,for example, an automotive manufacturer may elect to use the system ofthis invention for the automobile safety system and later expand it toinclude other devices. The data, in digital form, is carried on acarrier frequency, or as pulse data as in the Ethernet protocol, and isseparated at each device using either a microprocessor, “high-sidedriver” or other similar electronic circuit. Each device will have aunique, individualized address and be capable of responding to a messagesent with its address. A standard protocol will be implemented such asSAE J1850 where applicable. The return can be through vehicle groundcomprising the vehicle sheet metal and chassis or through a wire.

The advantages of such a system when fully implemented are numerous,among which the following should be mentioned:

1. The amount of wire in the vehicle will be substantially reduced.There is currently about 500 or more meters of wire in a vehicle.

2. The number and complexity of connectors will be substantiallyreduced. There are currently typically about 1000 pin connections in avehicle. When disconnection is not required, a sealed permanentconnector will be used to join wires in, for example, a T connection. Onthe other hand, when disconnection is required, a single or dualconductor connector is all that is required and the same connector canbe used throughout the vehicle. Thus, there will be only one or twouniversal connector designs on the vehicle.

3. The number of electronic modules will be substantially reduced andmaybe even be completely eliminated. Since each device will have its ownmicroprocessor, zone modules, for example, will be unnecessary.

4. Installation in the vehicle will be substantially easier since asingle conductor, with branches where required, will replace themulti-conductor wire harnesses currently used. Wire “choke points” willbe eliminated.

5. Reliability will be increased based on system simplicity.

6. Two way or bi-directional communication is enabled between alldevices. This simplifies OBD2 (On Board Diagnostic Level 2 now requiredby the U.S. Government for pollution control) installation, for example.

7. All devices on the vehicle are diagnosed on key-on. The driver ismade aware of all burned out lamps, for example before he or she startsthe vehicle.

8. Devices can be located at optimum places. A side impact sensor can beplaced within the vehicle door and still communicate with an airbagmodule located in the seat, for example, with high reliability andwithout installation of separate wiring. In fact, only a single or dualwire is required to connect all of the switches, sensors, actuators andother devices in the vehicle door with the remainder of the vehicleelectrical system.

9. Electro-magnetic interference (EMI) Problems are eliminated. Thedriver airbag system, for example would have the final circuit thatdeploys the airbag located inside the airbag module and activated whenthe proper addressed signal is received. Such a circuit would have anaddress recognition as well as diagnostic capabilities and might beknown as a “smart inflator”. EMI, which can now cause an inadvertentairbag deployment, ceases to be a problem.

10. Vehicle repair is simplified and made more reliable.

It is important that any wire used in this embodiment of the inventionbe designed so that it won't break even in an accident since if thesingle bus breaks the results can be catastrophic. Additionally, themain bus wire or pair of wires can be in the form of a loop around thevehicle with each device receiving its messages from either directionsuch that a single major break can be tolerated. Alternately, a tree orother convenient structure can be used and configured so that at most asingle branch of the network is disabled.

It should be understood that with all devices having access to thenetwork, there is an issue of what happens if many devices areattempting to transmit data and a critical event occurs, such as a crashof the vehicle, where time is critical, i.e., will the deployment of anairbag be delayed by this process. However, it is emphasized thatalthough the precise protocol has not yet been determined pendingconsultation with a customer, protocols do exist which solve thisproblem. For example, a token ring or token slot network where certaincritical functions are given the token more frequently than non-criticalfunctions and where the critical device can retain the token when acritical event is in progress is one solution. A crash sensor, forexample, knows that a crash is in progress before it determines that thecrash severity requires airbag deployment. That information can then beused to allocate the bandwidth to the crash sensor. An alternateapproach is to use a spread spectrum system whereby each device sendsand is responsive to a pattern of data that is sorted out usingcorrelation techniques permitting any device to send and receive atanytime regardless of the activity of any other device on the network.

Another issue of concern is the impact of vehicle noise on the network.In this regard, since every device will be capable of bi-directionalcommunication, standard error checking and correction algorithms areemployed. Each device is designed to acknowledge receipt of acommunication or the communication will be sent again until such time asreceipt thereof by the device is acknowledged. Calculations show thatthe bandwidth available on a single or dual conductor is much greaterthan required to carry all of the foreseeable communication requiredwithin an automobile. Thus, many communication failures can betolerated.

Furthermore, an airbag deployment system for a vehicle in accordancewith the invention disclosed above comprises a module housing, an airbagassociated with the housing, an inflator or inflator assembly arrangedin the housing for inflating the airbag, and an inflation determiningsystem for generating a signal indicative of whether deployment of theairbag is desired. The inflation determining system preferably comprisesone or more crash sensors, at least one of which is arranged separateand at a location apart from the housing. An electronic controller isarranged in or adjacent the housing and coupled to the inflationdetermining system. The controller controls inflation of the airbag bythe inflator assembly in response to the signal generated by theinflation determining system. An electrical bus electrically couples thecontroller and the inflation determining system whereby the signal fromthe inflation determining system is sent over the bus to the controllerto enable inflation of the airbag. The bus may consists of a single pairof wires over which power and information is conveyed. A sensor anddiagnostic module is also coupled to the bus for monitoring thecontroller. The inflation determining system, e.g., crash sensor, isdesigned to preferably generate a coded signal when deployment of theairbag is desired which coded signal is conveyed over the bus to thecontroller to enable the controller to control inflation of the airbagby the inflator assembly based thereon. The controller will preferablyinclude a power supply for enabling initiation of the inflator assembly.An occupant position sensor, e.g., an ultrasonic transmitter/receiverpair, may be arranged to detect the position of the occupant to beprotected by the airbag in which case, the controller would controlinflation of the airbag by the inflator assembly in consideration of thedetected position of the occupant. The occupant position sensor may bearranged in the same housing as the inflator assembly, airbag andcontroller.

An embodiment of an occupant protection system in accordance with theinvention comprises a plurality of occupant protection devices, eachcomprising a housing and a component deployable to provide protectionfor the occupant (such as an airbag), and a deployment determiningsystem for generating a signal indicating for which of the deployablecomponents deployment is desired, e.g., one or more crash sensors whichmay be located around the vehicle and preferably separate and atlocations apart from the same housings as the deployable components. Anelectronic controller is arranged in, proximate or adjacent each housingand coupled to the deployment determining system. Each controllercontrols deployment of the deployable component of the respectiveoccupant protection device in response to the signal generated by thedeployment determining system. An electrical bus electrically couplesthe controllers and deployment determining system so that the signalfrom the deployment determining system is sent over the bus to thecontrollers to enable deployment of the deployable components. A sensorand diagnostic module may be coupled to the bus for monitoring thecontrollers. The deployment determining system preferably generates acoded signal when deployment of one or more of the deployable componentsis desired so that since each controller initiates deployment of therespective deployable component only if the coded signal contains aspecific initiation code associated with the controller. An occupantposition sensor could also be provided to detect the position of theoccupant to be protected by the deployable components so that thecontroller of any of the deployable components would control deploymentthereof in consideration of the detected position of the occupant.

One embodiment of an occupant protection system, for a vehicle inaccordance with the invention comprises an occupant protection devicefor protecting an occupant in the event of a crash involving thevehicle, an initiation system for initiating deployment of the occupantprotection device, a power unit for storing sufficient energy to enablethe initiation system to initiate deployment of the occupant protectiondevice, an electronic controller connected to the power unit formonitoring voltage thereof and controlling the initiation system, adiagnostic module arranged to receive a signal from the controller as towhether the voltage of the power unit is sufficient to enable theinitiation system to initiate deployment of the occupant protectiondevice, and an electrical bus electrically coupling the controller andthe diagnostic module. The controller is arranged to generate a faultcode in the event of a failure of the power unit or the initiationsystem, which fault code is sent to the diagnostic module over the bus.One or more crash sensors or other deployment determining system arepreferably coupled to the bus for generating a (coded) signal indicativeof whether deployment of the occupant protection device is desired, thesignal being sent from the determining system over the bus to thecontroller. The controller may be arranged in the housing or adjacentthe housing.

Another embodiment of an occupant protection system in accordance withthe invention comprises a deployable occupant protection device, adeployment determining system for generating a coded signal indicativeof whether deployment of the occupant protection device is desired, andan electrical bus electrically coupling the occupant protection deviceand the deployment determining system. The coded signal from thedeployment determining system is sent over the bus to the occupantprotection device to enable deployment of the occupant protectiondevice. The deployment determining system may comprise one or more crashsensors arranged separate and at locations apart from the occupantprotection device. A controller may be coupled to the deploymentdetermining system, the occupant protection device and the bus, andcontrols deployment of the occupant protection device in response to thecoded signal generated by the deployment determining system. The codedsignal from the deployment determining system is sent over the bus tothe controller to enable deployment of the occupant protection device.

A method for controlling deployment of an occupant protection system forprotecting an occupant in a vehicle comprises arranging a deployableoccupant protection device in the vehicle, generating a coded signalindicative of whether deployment of the occupant protection device isdesired, electrically coupling the occupant protection device and thecrash sensor by means of an electrical bus, and directing the codedsignal from the crash sensor over the bus to the occupant protectiondevice to enable deployment of the occupant protection device. The codedsignal may be generated by a crash sensor in response to a crash of thevehicle for which deployment of the occupant protection device might berequired.

Although several preferred embodiments are illustrated and describedabove, there are possible combinations using other geometries, materialsand different dimensions for the components that perform the samefunctions as described and illustrated herein. This invention is notlimited to the above embodiments and should be determined by thefollowing claims. For example, the reducing system for reducing theconcentration of toxic gas in the passenger compartment of the vehiclein conjunction with deployment of the at least one airbag may be coupledto an element of the airbag module which would indicate deployment ofthe airbag or may be a completely separate system which is positioned todetect or sense deployment of the air bag and activate accordingly.Also, for example, although the airbag is described as being a filmairbag, it must be understood that this is only a preferred embodimentand that the airbag can be made of any other material, even though thismay detract from efficient operation of the airbag module. A variety ofdifferent processes for inflating an airbag so as to provide a highpumping ratio, i.e., a high ratio of gas from the passenger compartmentto pressurized gas from the inflator, as well as to achieve the numerousobjects mentioned above, are also within the scope of the inventiondisclosed herein as are different configurations of the electroniccircuits. It is quite possible to house the passenger side electroniccircuit within the passenger module instead of adjacent to it and it isalso possible to house the electronic circuitry within either thepassenger or driver electronic circuitry.

Described above is an airbag for a vehicle which includes a plurality ofsections of material joined to one another, e.g., heat-sealed oradhesively-sealed, to form a plurality of substantially interconnectedcompartments receivable of an inflating medium. The sections of materialmay be discrete sheets of film with optional tear propagation arrestingstructure. Two or more of the sections of material may be at leastpartially in opposed relationship to one another and then joined to oneanother at locations other than at a periphery of any of the sections tothereby form the interconnected compartments between the sections ofmaterial. The sections of material may be joined to one another alongparallel or curved lines or links to thereby form the interconnectedcompartments between the sections of material, which when inflated, willbe cellular or tubular.

Also described above is an inflatable occupant protection system whichincludes a housing mounted in the vehicle and having an interior, adeployable inflatable element or airbag contained within the housinginterior prior to deployment, an inflator coupled to the housing forinflating the airbag (such as a gas generator for supplying a gas intothe interior of the airbag), the airbag being attached to and in fluidcommunication with the inflator, and an initiator for initiating the gasgenerator to supply the gas into the interior of the airbag in responseto a crash of the vehicle, i.e., a crash sensor. The airbag may be asdescribed in the paragraphs above. The housing may be elongate andextends substantially along the entire side of the vehicle such that theairbag is arranged to inflate between a side of the vehicle and therespective spaces above both the front and rear seats. In anotherimplementation, the housing is arranged in the front seat and extendsbetween sides of the vehicle such that the airbag is arranged to inflateoutward from the front seat toward the rear seat.

Also disclosed is a method for manufacturing an airbag for a vehicle inwhich a plurality of sections of material are joined together to form aplurality of interconnected compartments, e.g., by applying an adhesivebetween opposed surfaces of the sections of material to be joinedtogether or heating the sections of material to be joined together. Thesections of material may be joined together along parallel or curvedlines to form straight or curved, elongate interconnected compartmentswhich become tubular or cellular when inflated with a gas.

The tear propagation arresting structure for the film sheets may be (i)the incorporation of an elastomeric film material, a laminated fabric,or net, which are connected to each of the pieces of plastic film (e.g.,the inelastic film which provides the desired shape upon deployment ofthe airbag), or (ii) means incorporated into the formulation of theplastic film material itself. Also, the two pieces of film may be formedas one integral piece by a blow molding or similar thermal forming orlaminating process.

In accordance with another embodiment of the invention, an airbag has acoating composition which contains substantially dispersed exfoliatedlayered silicates in an elastomeric polymer. This coating, when dry,results in an elastomeric barrier with a high effective aspect ratio andimproved permeability characteristics, i.e., a greater increase in thereduction of permeability of the coating. Drying may occur naturallyover time and exposure to air or through the application of heat. Thisis a further use of a plastic film where although the mechanicalproperties of the base material are not altered the flow propertiesthrough the material are.

The airbag is optionally made of fabric and can take any form includingthose in the prior art. For example, if a side curtain airbag, then theairbag can define a series of tubular gas-receiving compartments, oranother series of compartments. The side curtain airbag can be arrangedin a housing mounted along the side of the vehicle, possibly entirelyabove the window of the vehicle or partially along the A-pillar of thevehicle.

The side curtain airbag includes opposed sections or layers of material,either several pieces of material joined together at opposed locationsor a single piece of material folded over onto itself and then joined atopposed locations. Gas is directed into the compartments from a gasgenerator or a source of pressurized gas. Possible side curtain airbagsinclude those disclosed in the current assignee's U.S. Pat. Nos.5,863,068, 6,149,194 and 6,250,668.

The invention is not limited to side curtain fabric airbags and otherfabric airbags are also envisioned as being encompassed by theinvention. Also, it is conceivable that airbags may be made of materialsother than fabric and used with a barrier coating such as any of thosedisclosed herein and other barrier coatings which may be manufacturedusing the teachings of this invention or other inventions relates tobarrier coatings for objects other than airbags. Thus, the invention canencompass the use of a barrier coating for an airbag, regardless of thematerial of the airbag and its placement on the vehicle.

In one aspect, the present invention provides a side curtain airbagincluding one or more sheets of fabric that contains air or a gas underpressure, and having on an interior or exterior surface of the fabricsheet(s) a barrier coating formed by applying to the surface a mixturecomprising in a carrier liquid an elastomeric polymer, a dispersedexfoliated layered platelet filler preferably having an aspect ratiogreater than about 25 and optionally at least one surfactant. The solidscontent of the mixture is optionally less than about 30% and the ratioof polymer to the filler is optionally between about 20:1 and about 1:1.The coating may be dried on the coated surface, wherein the driedbarrier coating has the same polymer to filler ratio as in the mixtureand provides an at least 5-fold greater reduction in gas, vapor,moisture or chemical permeability than a coating formed of the unfilledpolymer alone.

In a preferred embodiment, the fabric is coated with a barrier coatingmixture, which contains the polymer at between about 1% to about 30% inliquid form and between about 45% to about 95% by weight in the driedcoating. The dispersed layered filler is present in the liquid coatingmixture at between about 1% to about 10% by weight, and in the driedcoating formed thereby, at between about 5% to about 55% by weight. Thedried coating, in which the filler exhibits an effective aspect ratio ofgreater than about 25, and preferably greater than about 100, reducesthe gas, vapor or chemical permeability greater than 5-fold that of thedried, unfilled polymer alone.

In another preferred embodiment, the invention provides a fabric sidecurtain airbag coated with a preferred barrier coating mixture which hasa solids contents of between about 5% to about 15% by weight, andcomprises in its dried state between about 65% to about 90% by weight ofa butyl rubber latex, between about 10% to about 35% by weight of alayered filler, desirably vermiculite, and between about 0.1% to about15% by weight of a surfactant.

In another embodiment, the invention provides a fabric side curtainairbag on a surface or at the interface of two surfaces therein a driedbarrier coating formed by a barrier coating mixture comprising in acarrier liquid, an elastomeric polymer, a dispersed exfoliated layeredplatelet filler preferably having an aspect ratio greater than about 25and optionally at least one surfactant, wherein the solids content ofthe mixture may be less than about 30% and the ratio of polymer to thefiller is optionally between about 20:1 and about 1:1. When dried, thecoating optionally comprises about 45% to about 95% by weight of thepolymer, between about 5% to about 55% by weight the dispersed layeredfiller; and between about 1.0% to about 15% by weight the surfactant.The coating on the article, in which the filler exhibits an effectiveaspect ratio of greater than about 25, preferably greater than about100, reduces the gas, vapor or chemical permeability of the airbaggreater than 5-fold the permeability of the airbag coated with thepolymer alone.

In still another embodiment, the invention provides a fabric sidecurtain airbag having on a surface or at the interface of two surfacestherein a dried barrier coating formed by a barrier coating mixturecomprising in a carrier liquid, a butyl-containing polymer latex, adispersed exfoliated layered vermiculite filler preferably having anaspect ratio about 1000 or greater; and optionally at least onesurfactant. The solids content of the mixture may be less than about 17%and the ratio of the polymer to the filler may be between about 20:1 andabout 1:1.

In a preferred embodiment, the coating mixture has a solids content ofbetween about 5% to about 15% by weight, and forms a dried coating onthe surface that comprises between about 65% to about 90% by weight thebutyl-containing polymer, between about 10% to about 35% by weight thevermiculite filler, and between about 1.0% to about 15% by weight thesurfactant. The coating on the inflated product in which the fillerexhibits an effective aspect ratio of greater than about 25, preferablygreater than about 100, reduces the gas, vapor or chemical permeabilityof the airbag greater than 5-fold the permeability of the article coatedwith the polymer alone.

In still a further embodiment, the invention provides a method formaking a fabric side curtain airbag, the method involving coating asurface of the fabric airbag with, or introducing into the interfacebetween two surfaces of the fabric airbag, an above-described barriercoating mixture.

One method for manufacturing an airbag module including an airbag inaccordance with the invention entails applying to a surface of asubstrate a solution comprising an elastomeric polymer and a dispersedexfoliated layered filler and causing the solution to dry to therebyform a barrier coating on the substrate, forming an airbag having anedge defining an entry opening for enabling the inflation of the airbagfrom the substrate having the barrier coating thereon, arranging theairbag in a housing, sealing the edge of the airbag to the housing andproviding a flow communication in the housing to allow inflation fluidto pass through the entry opening into the airbag. The airbag ispreferably folded in the housing. The airbag may be formed by cuttingthe substrate to the desired shape and size.

Another method for manufacturing an airbag module entails applying to asurface of a first substrate a solution comprising an elastomericpolymer and a dispersed exfoliated layered filler, covering the solutionwith a second substrate, causing the solution to dry to thereby form abarrier coating between the first and second substrates, forming anairbag having an edge defining an entry opening for enabling theinflation of the airbag from the first and second substrates having thebarrier coating therebetween, arranging the airbag in a housing andsealing the edge of the airbag to the housing. Further, a flowcommunication is provided in the housing to allow inflation fluid topass through the entry opening into the airbag. The airbag may be foldedin the housing. The formation of the airbag may involve cutting thefirst and second substrates having the barrier coating therebetween.

Another method for forming an airbag, in particular a side curtainairbag or another type of airbag made of a first piece for fabricconstituting a front panel of the airbag and a second piece of fabricconstituting a rear panel of the airbag, entails heat or adhesivesealing the first and second pieces of fabric together over an extendedseam width to form an airbag while maintaining an entry opening forpassage of inflation fluid into an interior of the airbag andpartitioning the airbag along partition lines into a plurality ofchambers each receivable of the inflation fluid. The location of thepartition lines is determined to prevent concentration of stress in theseams, e.g., by analyzing the airbag using finite element analysis asdescribed in Appendix 1 herein and Appendices 1-6 of the '379application. The first and second pieces of fabric may be coated with abarrier coating.

Still another method for forming an airbag in accordance with theinvention comprises the steps of providing a plurality of layers ofmaterial, interweaving, heat sealing or sewing the layers together toform the airbag while maintaining an entry opening for passage ofinflation fluid into an interior of the airbag and coating the airbagwith a barrier coating. The airbag may be a side airbag with front andrear panel joined together over an extended seam width. As such, it ispossible to partition the airbag along partition lines into a pluralityof chambers each receivable of the inflation fluid and determine thelocation of the partition lines to prevent concentration of stress inthe seams.

There has thus been shown and described an airbag system with aself-limiting and self-shaping airbag which fulfills all the objects andadvantages sought after. Further, there has been shown and described anairbag system with a film airbag utilizing a film material whichcomprises at least one layer of a thermoplastic elastomer film materialwhich fulfills all the objects and advantages sought after. Manychanges, modifications, variations and other uses and applications ofthe subject invention will, however, become apparent to those skilled inthe art after considering this specification and the accompanyingdrawings which disclose the preferred embodiments thereof. All suchchanges, modifications, variations and other uses and applications whichdo not depart from the spirit and scope of the invention are deemed tobe covered by the invention which is limited only by the followingclaims. For example, the present invention describes numerous differentairbag constructions as well as different methods for fabricatingairbags. It is within the scope of the invention that all of thedisclosed airbags can, for the most part, be made by any of the methodsdisclosed herein. Thus, in one typical process for constructing a filmairbag having at least two compartments, either isolated from oneanother, within one another or in flow communication with each other, atleast one flat panel of film airbag material is provided and thenmanipulated, processed or worked to form the different compartments.More particularly, the flat panel is joined at appropriate locations toform the different compartments, e.g., by heat sealing or an adhesive.The compartments may be any shape disclosed herein, e.g.,tubular-shaped.

With respect to the construction of the airbag as shown in FIGS. 74C and74D, another method of obtaining the airbag with a variable thickness isto provide an initial, substantially uniformly thick film substrate(inelastic film) and thereafter applying a coating (a thermoplasticelastomer) thereon in predetermined locations on the substrate,preferably in an organized predetermined pattern, such that it ispossible to obtain thicker portions in comparison to other uncoatedportions. In this manner, the film airbag can be provided with distinctthicknesses at different locations, e.g., thicker portions whichconstitute rings and ribs (i.e., the polar symmetric pattern of FIG.74C), or only at specific locations where it is determined that higherstresses arise during deployment for which reinforcements by means ofthe thicker film is desired. An alternative fabrication method would beto produce the airbag from thermoplastic elastomeric material with aninitial varying thickness as well as a layer of inelastic film toprovide the airbag with the desired shape. In this regard,plastic-manufacturing equipment currently exists to generate a plasticsheet with a variable thickness. Such equipment could be operated toprovide an airbag having thicker portions arranged in rings and ribs asshown in FIG. 74C.

The limiting net described above may be used to limit the deployment ofany and all of the airbags described herein, including embodimentswherein there is only a single airbag.

This application is one in a series of applications covering safety andother systems for vehicles and other uses. The disclosure herein goesbeyond that needed to support the claims of the particular inventionthat is claimed herein. This is not to be construed that the inventorsare thereby releasing the unclaimed disclosure and subject matter intothe public domain. Rather, it is intended that patent applications havebeen or will be filed to cover all of the subject matter disclosedabove.

The inventions described above are, of course, susceptible to manyvariations, modifications and changes, all of which are within the skillof the art. It should be understood that all such variations,modifications and changes are within the spirit and scope of theinventions and of the appended claims. Similarly, it will be understoodthat applicant intends to cover and claim all changes, modifications andvariations of the examples of the preferred embodiments of the inventionherein disclosed for the purpose of illustration which do not constitutedepartures from the spirit and scope of the present invention asclaimed.

Although several preferred embodiments are illustrated and describedabove, there are possible combinations using other geometries, materialsand different dimensions for the components and different forms of theneural network implementation that perform the same functions. Also, theneural network has been described as an example of one patternrecognition system. Other pattern recognition systems exist and stillothers are under development and will be available in the future. Such asystem can be used to identify crashes requiring the deployment of anoccupant restraint system and then, optionally coupled with additionalinformation related to the occupant, for example, create a system thatsatisfies the requirements of one of the Smart Airbag Phases. Also, withthe neural network system described above, the input data to the networkmay be data which has been pre-processed rather than the rawacceleration data either through a process called “feature extraction”,as described in Green (U.S. Pat. No. 4,906,940) for example, or byintegrating the data and inputting the velocity data to the system, forexample. This invention is not limited to the above embodiments andshould be determined by the following claims.

Appendix 1: Analysis of Aspiration Nozzle

Gas at high pressure and temperature is generated in the chamber of theinflator. This gas flows through a convergent-divergent nozzle, toemerge near the throat of a larger convergent-divergent nozzle. Bothnozzles are two-dimensional and symmetric about the center plane.Passenger compartment air enters the larger nozzle and begins to mixwith the inflator gas where the inflator gas emerges from its nozzle. Atthe end of a mixing section the two streams are substantially uniformlymixed. The mixing section is followed by a divergent section where someof the velocity of the mixed stream is converted back into pressuresufficient to fill the airbag.

The inflator gas emerges from its nozzle as a supersonic jet at highspeed and relatively low static pressure and temperature. As the jetmixes with the surrounding air it entrains this air, imparting some ofits high kinetic energy to the combined stream. The techniques requiredfor analysis of this process are contained in the book The Theory ofTurbulent Jets by G. N. Abramovich (The M.I.T. Press, Cambridge Mass.,1963). The basic technique is to reduce the full three- orfour-dimensional equations of transient fluid flow by integrating themover the cross-section. This is supplemented by additionalapproximations justified by theory and experiment.

The equations of fluid flow may be expressed as conservation of mass,momentum, and energy. Let

x be the distance along the central plane from the exit of the inflatorgas nozzle, in the direction of flow, y be the distance from the centralplane, b be the value of y at the boundary of the jet, C_(p) be thefluid heat capacity at constant pressure, u be the time-averaged fluidspeed in the x-direction, p be the fluid static pressure, T be the(absolute) static temperature of the fluid, h be the fluid enthalpy, ρbe the fluid mass density, R be the gas constant, γ be the specific heatratio of the fluid, μ be the fluid viscosity, k be the fluid thermalconductivity, m′ be the mass flow rate per unit width (per unit z) ofthe inflator, q′ be the heat input rate per unit width of the inflatornozzle, n be the aspiration ratio, the ratio of the mass flow rate ofair to the mass flow rate of the inflator gas, f be the fanning frictionfactor, h_(c) be the heat transfer coefficient, based on the adiabaticsaturation temperature, Pr be the Prandtl number, Re be the Reynoldsnumber, St be the Stanton number.

The following subscripts are used:

m for the central plane (inside the jet), H for the fluid outside thejet (air), w for the fluid adjacent to the wall of the outer nozzle, orfor the wall of the inner nozzle, 0 for the cross-section where thesupersonic inflator gas jet emerges (the beginning of the mixingsection), 2 for the end of the mixing section, 3 for the exit from theair nozzle (airbag entrance), t for total (stagnation) properties, a forambient conditions, inside the vehicle, i for pressure and temperatureinside the inflator, before expansion, * for the throat of theconvergent-divergent inflator exit nozzle, as for adiabatic saturation(temperature), ref for properties or numbers evaluated at the referencetemperature, bag for fluid properties inside the airbag.

Note that b₀ is the half-thickness of the supersonic inflator gas nozzleat its exit.

Then after integrating over the cross-section the conservation equationsfor steady flow become

$\begin{matrix}{{Momentum}\text{:}\mspace{14mu}\begin{matrix}{{\int_{0}^{y_{w}}{\rho\; u^{2}{\mathbb{d}y}}} = {{\rho_{m\; 0}u_{m\; 0}^{2}b_{0}} + {\rho_{H\; 0}{u_{H\; 0}^{2}\left( {y_{w\; 0} - b_{0}} \right)}} +}} \\{{b_{0}p_{m\; 0}} + {\left( {y_{w\; 0} - b_{0}} \right)p_{H\; 0}} + {\int_{0}^{x}{p_{w}{\mathbb{d}y_{w}}}} - {\int_{0}^{y_{w}}{p{{\mathbb{d}y}.}}}}\end{matrix}} & 1 \\{{{Mass}\text{:}\mspace{11mu}{\int_{0}^{y_{w}}{\rho\; u{\mathbb{d}y}}}} = {{\rho_{m\; 0}u_{m\; 0}b_{0}} + {\rho_{H\; 0}{{u_{H\; 0}\left( {y_{w\; 0} - b_{0}} \right)}.}}}} & 2 \\{{{Energy}\text{:}\mspace{11mu}{\int_{0}^{y_{w}}{\rho\; u\; h_{t}}}} = {{\rho_{m\; 0}u_{m\; 0}h_{{mt}\; 0}} + {\rho_{H\; 0}u_{H\; 0}{{h_{H\; t\; 0}\left( {y_{w\; 0} - b_{0}} \right)}.}}}} & 3 \\{{m_{m}^{\prime} = {2\rho_{m\; 0}u_{m\; 0}b_{0}}},\;{m_{H}^{\prime} = {2\rho_{H\; 0}{u_{H\; 0}\left( {y_{w\; 0} - b_{0}} \right)}}},\;{m^{\prime} = {m_{m}^{\prime} + m_{H}^{\prime}}},} & 4\end{matrix}$

The approximations have been made that the conditions (velocity,temperature, pressure) in the two streams are each substantially uniformat the cross-section where they meet that time-averaged fluid velocitycomponents in the cross-directions are much smaller than in the axialdirection, and that the friction and heat transfer at the wall in theouter nozzle may be neglected. These approximations may be relaxed, andwill be in later studies, but should have a secondary effect on theresults of interest.

Abramovich provides expressions for the velocity and total temperatureprofiles in the jet in terms of the values on the mid-plane and in thesurrounding air. These can be substituted in the conservation equations,along with expressions for the air properties in terms of the pressure,to provide 3 equations for the axial distribution of mid-plane velocity,mid-plane temperature, and pressure. This calculation will be necessaryto determine the effect of the finite length of the mixing section andto find the optimum length. An approximation to the overall performanceof the aspirator can be found more simply if the flow is assumed to befully mixed and substantially uniform at the end of the mixing length.Further approximations in this preliminary analysis are that in the airnozzle and in the mixing section the fluids are perfect gases withconstant specific heats, that the two streams have the same properties,those of air,

$\begin{matrix}{{p = {\rho\;{RT}}},\;{C_{p} = \frac{\gamma\; R}{\gamma - 1}},\;{h = {C_{p}T}},} & 5\end{matrix}$

that the air flow up to the point where mixing begins is isentropic, so

$\begin{matrix}{{\rho_{H\; 0} = {\frac{p_{a}}{{RT}_{a}}\left( \frac{p_{H\; 0}}{p_{a}} \right)^{\frac{1}{\gamma}}}},{u_{H\; 0}^{2} = {2\; C_{p}{T_{a}\left\lbrack {1 - \left( \frac{p_{H\; 0}}{p_{a}} \right)^{1 - \frac{1}{\gamma}}} \right\rbrack}}},} & 6\end{matrix}$

and that y_(w) is constant in the mixing region, from x=0 to the sectionwhere the flow is substantially uniform again, say at section 2. Thenthe 3 conservation equations may be written

$\begin{matrix}{{{\rho_{2}u_{2}y_{w}} = {{\rho_{m\; 0}u_{m\; 0}b_{0}} + {\rho_{H\; 0}{u_{H\; 0}\left( {y_{w} - b_{0}} \right)}}}},{{\rho_{2}u_{2}^{2}y_{w}} = {{\rho_{m\; 0}u_{m\; 0}^{2}b_{0}} + {\rho_{H\; 0}{u_{H\; 0}^{2}\left( {y_{w} - b_{0}} \right)}} + {b_{0}p_{m\; 0}} + {\left( {y_{w} - b_{0}} \right)p_{H\; 0}} - {y_{w}p_{2}}}},{{\rho_{2}u_{2}T_{2t}y_{w}} = {{\rho_{m\; 0}u_{m\; 0}T_{{mt}\; 0}b_{0}} + {\rho_{H\; 0}u_{H\; 0}{{T_{a}\left( {y_{w} - b_{0}} \right)}.}}}}} & 7\end{matrix}$

If the gas temperature in the inflator is relatively low, say less than2000 F, then equations similar to Eqs. (6) may be used for the inflatornozzle in the preliminary analysis, without introducing errors thatcannot be adjusted for later. Sufficient aspiration can be achieved sothat the airbag temperature is not excessive. When the inflatortemperature is much higher, though, then the inflator gas must becooled. The inflator gas exit nozzle is, as will be seen, quite thin(small b), and as a result the heat transfer, and, to a lesser extent,the wall fluid friction is significant unless the nozzle is very short.Thus the nozzle is a natural place to cool the hot gases from theinflator.

Flow in the nozzle will be assumed to be turbulent. The fluid flow andheat transfer equations are taken to be (see, for example, F. Kreith,Principles of Heat Transfer, 3rd ed. (Harper & Row, New York, 1973),Chapters 6 and 8, and M. Jakob, Heat Transfer, vol. 1 (John Wiley, NewYork, 1949).

$\begin{matrix}{{{m_{m}^{\prime}C_{p\; t}\frac{\mathbb{d}T_{t}}{\mathbb{d}x}} = {\frac{\mathbb{d}q^{\prime}}{\mathbb{d}x} = {{- 2}{h_{e}\left( {T_{as} - T_{w}} \right)}}}},{T_{as} = {T + {\left( {T_{t} - T} \right)\Pr_{ref}^{1/3}}}},{{{\frac{1}{\rho}\frac{\mathbb{d}p}{\mathbb{d}x}} + \frac{\mathbb{d}\left( {u^{2}/2} \right)}{\mathbb{d}x}} = {{- f}\;\frac{u^{2}}{2}\frac{4}{4b}}},{f = {0.046\;{Re}_{ref}^{- 0.2}}},{\frac{h_{e}}{C_{p,{ref}}\rho\; u} = {{St}_{ref} = {\frac{1}{2}f\;\Pr_{ref}^{{- 2}/3}}}},{T_{ref} = {{\frac{1}{2}\left( {T + T_{w}} \right)} + {0.22\left( {T_{as} - T} \right)}}},{{Re}_{ref} = \frac{2m_{m}^{\prime}}{\mu_{ref}}},{\Pr_{ref} - {\frac{C_{p,{ref}}\mu_{ref}}{k_{ref}}.}}} & 8\end{matrix}$

Some of these may be combined to yield the following equations for therates of change of velocity and total temperature

$\begin{matrix}{{\frac{\mathbb{d}u}{\mathbb{d}x} = {{{- \frac{2b}{m_{m}^{\prime}}}\frac{\mathbb{d}p}{\mathbb{d}x}} - \frac{fu}{2b}}},{\frac{\mathbb{d}T_{t}}{\mathbb{d}x} = {{- \frac{C_{p,{ref}}}{C_{p\; t}}}{{\frac{{St}_{ref}}{b}\left\lbrack {T_{t} - T_{w} - {\left( {1 - \Pr_{ref}^{1/3}} \right)\left( {T_{t} - T} \right)}} \right\rbrack}.}}}} & 8\end{matrix}$

The temperature dependence of the specific heat of air was taken fromNACA Report 1135, Equations, Tables, and Charts for Compressible Flow(U.S. Govt. Printing Office, Washington, 1953) p. 15 (thermallyperfect); the temperature dependencies of the viscosity and thermalconductivity were found by fitting Sutherland-type equations (S. Chapman& T. G. Cowling, The Mathematical Theory of Non-Uniform Gases (CUP,Cambridge, 1961), pp. 224 and 241) to data from Kreith p. 636:

$\begin{matrix}{{C_{p} = {3.5R\left\{ {1 + {\frac{2}{7}\left\lbrack {\left( \frac{5500}{T} \right)^{2}\frac{{\mathbb{e}}^{5500/T}}{\left( {{\mathbb{e}}^{5500/T} - 1} \right)^{2}}} \right\rbrack}} \right\}}},{\mu = {3.564 \times 10^{- 6}\frac{T^{1.314}}{T + 594.8}\mspace{11mu}{lb}_{m}\text{/}{ft}\text{-}\sec}},{k = {4.113 \times 10^{- 7}\frac{\left( {T + 429900} \right)T^{0.9576}}{T + 4452}{Btu}\text{/}{ft}\text{-}{hr}\text{-}{R.}}}} & 9\end{matrix}$

Now suppose that the pressure and temperature in the inflator, p_(i) andT_(i), and the ambient pressure and temperature, p_(a) and T_(a), arespecified, along with the airbag pressure p_(bag), the desired airbagtemperature T_(bag), the airbag inflated volume V_(bag), the airbag filltime, and the width of the inflator nozzle. The airbag pressure,temperature, volume, and fill time allow the total mass flow rate m tobe calculated, and dividing this by the width gives the required m′. Ifheat loss from the inflator gas is ignored then the required aspirationratio is given by

$\begin{matrix}{n = {\frac{T_{i} - T_{bag}}{T_{bag} - T_{a}}.}} & \left( {11a} \right)\end{matrix}$

If the inflator temperature is too high, then the inflator exit nozzlemay be designed to achieve some exit total temperature T_(mt0) and theaspiration ratio becomes

$\begin{matrix}{n = {\frac{T_{{mt}\; 0} - T_{bag}}{T_{bag} - T_{a}}.}} & \left( {11b} \right)\end{matrix}$

Then m′_(m)=m′/(1+n) and m′_(H)=nm′_(m).

The inflator exit nozzle may be designed to produce any reasonablepressure p_(m0) at its exit, regardless of the air pressure at thatpoint.

When the inflator temperature is relatively low, the inflator exitnozzle design is approximated by assuming isentropic flow. Equationssimilar to Eqs. (6) are used to calculate the density and velocity ofthe inflator gas at the nozzle exit, section 0. When the inflatortemperature is high the inflator nozzle is designed by integrating Eqs.(9) numerically, using the relations of Eqs. (8) and (10). For this thenozzle wall temperature, and an entrance loss factor for the pressuredrop, must be specified. The shape was determined by requiring aconstant rate of pressure drop with axial distance, until the divergenceangle reached a preset maximum and then the divergence angle was held atthat value. Different pressure drop rates were tried until the desiredexit total temperature was reached. This procedure produces the inflatorgas density and velocity at the exit, along with the total temperature.

An air pressure at the start of the mixing section, p_(H0), may bechosen. Equations (6) then allow ρ_(H0) and u_(H0) to be calculated,along with the air nozzle size y_(w)−b₀.

Now Equations (7) may be used to find the properties at the end of themixing section. The first of Equations (7) allows the product ρ₂u₂ to becalculated, and the third of Equations (7) yields

$\begin{matrix}{T_{2t} = {\frac{T_{i} + {nT}_{a}}{1 + n}.{Now}}} & 12 \\{{u_{2}p_{2}} = {{u_{2}\rho_{2}{RT}_{2}} = {\rho_{2}u_{2}{R\left( {T_{2t} - \frac{u_{2}^{2}}{2C_{p}}} \right)}}}} & 13\end{matrix}$

and when this is used in the second of Equations (7) that equationbecomes a quadratic in u₂ with all other quantities known. The two rootsof this quadratic correspond to the two possibilities of either subsonicor supersonic flow at section 2. In practice the flow here will beexpected to be subsonic (that is, shocks will occur in the supersonicstream). Once u₂ is found, p₂ is calculated with Equation (113) andp_(2t) with

$\begin{matrix}{p_{2t} = {p_{2}\left\lbrack {1 - \frac{u_{2}^{2}}{2C_{p}T_{2t}}} \right\rbrack}^{- \frac{\gamma}{\gamma - 1}}} & 14\end{matrix}$

When the gas mixture comes to rest in the airbag its temperature will beT_(bag)=T_(2t) (neglecting heat lost to the airbag material).

In the divergent portion of the main nozzle, after section 2, some ofthe kinetic energy at section 2 is converted into an increase in staticpressure. If y_(w3) is the half-thickness at the exit from the divergentportion, and p₃ the pressure at the exit, then

$\begin{matrix}{\frac{y_{w\; 3}}{y_{w}} = {\left( \frac{p_{2}}{p_{3}} \right)^{\frac{1}{\gamma}}{\sqrt{\frac{1 - \left( \frac{p_{2}}{p_{2t}} \right)^{\frac{\gamma - 1}{\gamma}}}{1 - \left( \frac{p_{3}}{p_{2t}} \right)^{\frac{\gamma - 1}{\gamma}}}}.}}} & 15\end{matrix}$

p₃ will be the airbag pressure p_(bag).

If p_(bag), and y_(w3) are specified then the last series ofcalculations may be performed for different p_(H0) until the correctvalue is found for p_(H0). This will be the value that causes Equation(15) to be satisfied. Alternatively, if p_(2t) is greater than p_(bag),then the necessary value of y_(w3) may be computed.

When Equations (9) are integrated numerically then the thickness at theminimum section of the inflator nozzle will be evident. When the gasflow in the inflator nozzle is assumed to be isentropic, then thehalf-thickness at the throat of the convergent-divergent inflator exitnozzle is given by

$\begin{matrix}{\frac{b_{*}}{b_{0}} = {\sqrt{\frac{\gamma + 1}{\gamma - 1}}\left( \frac{\gamma + 1}{2} \right)^{\frac{1}{\gamma - 1}}\left( \frac{p_{m\; 0}}{p_{i}} \right)^{\frac{1}{\gamma}}{\sqrt{1 - \left( \frac{p_{m\; 0}}{p_{i}} \right)^{\frac{\gamma - 1}{\gamma}}}.}}} & 16\end{matrix}$

Appendix 2: Engineering Summary Report Anticipatory Sensor: ObjectRecognition

Introduction

The current revision of an anticipatory sensor contains two parts: acamera for an oncoming object recognition, and a radar (SLR) foridentifying the presence of the oncoming object, determining itsvelocity relative to the car and the latter's distance to the object.The following objects are grouped into different classes for thisproject: cars, trucks, motorcycles, barriers (different types), poles,and persons.

A goal of the anticipatory sensor development is to determine a severityof a possible crash. The goal will be achieved by detecting the object'stype, its oncoming velocity, and its distance to the protecting car.Using the detected parameters, an automatic system should select one ofpredefined algorithms of an airbag deployment to protect a passenger ofthe car.

The problem thus stated can be resolved by solving several independentproblems. The problems are: object recognition, detection of thevelocity and distance to the object. The first one is solved with datafrom the camera and the last two are solved using signals from SLR. Inits turn, the problem of an oncoming object recognition can be splitinto three cases:

1. A moving object and a motionless car (static case);

2. A motionless object and a moving car (one-sided or half-dynamiccase);

3. A moving object and a moving car (full dynamic case).

Because of a possibility to use several sequential pictures from thecamera during the object recognition, the worst or hardest case for theobject recognition is the second one. It is because the motionlessoncoming objects give the least variation of sizes or its boundarypositions on the pictures with respect to the background.

The current work is concentrated on a solution to the first case of theobject recognition problem. Among the objects of interest defined above,only four types of objects could be referred to this case: cars, trucks,motorcycles, and people. The last one is not interesting for thisparticular case because it is not dangerous for a passenger of the car.

For the first stage of the anticipatory sensor development, the staticcase for a “car vs. truck” recognition was selected.

1. Data collection

The current revision of the anticipatory sensor hardware consists of avideo camera with the resolution of 320×240 pixels and a radar (SLR) todetermine the distance and speed of the oncoming object.

For the data collection purpose, data collection software was developed(see “Anticipatory sensor data collection software specification”2003.1230.007/AG). The software continuously collects several sequentialimages from the camera and saves them as a pattern for recognition assoon as an object appears in the radar field of view (about 3-6 metersfrom the anticipatory sensor.) Therefore, for each object, there are atleast two camera shots and at least two radar scans (depending onspecified parameters). This data is synchronized in the sense that itbelong to the same object. Also, all radar scan data are accompaniedwith time stamps in order to be able to determine the object's speed.

The static case data collection (a moving object and a motionless car)was done with the anticipatory sensor placed on the road shoulder formotor vehicles driving along the nearest traffic lane. Motor vehiclesdriving along the other and the same traffic lanes are allowed to keepreal-world conditions.

Data was collected in the daytime for different object types and speedsof the objects. The weather varied from bright sun to all-over clouds.Object types are motor vehicles that differ in their purpose,manufacturer, color and size. Because of a different speed of thevehicles and settings in the data collection software, the distancesbetween the anticipatory sensor and the objects in the first savedpictures from the camera vary from 6 to 20 meters. The distance betweenthe sensor and an object on two sequential pictures varies also, and thevariation is ˜0.5-2 meters.

For the current investigation, 1620 shots were collected, eachconsisting of two sequential images from the camera. Among the shots,1044 were collected for trucks and 576 for cars.

Examples of the collected images are shown in FIGS. 128 and 129. FIGS.128 and 129 demonstrate a diversity of motor vehicles (cars 1 and trucks2) that are collected for this task.

2. Image Segmentation

An image segmentation algorithm is intended to find an object ofinterest in a picture. The picture can have a complex appearance and anarbitrary background. The profit of use the image segmentation comesfrom a simplification of further image processing and, finally, of theclassification task, too.

The following conditions were posed for the image segmentationalgorithm:

-   -   a) it should select a portion of an image which contains the        object;    -   b) the selected portion should include the whole object;    -   c) the selected portion should be as small as possible to        eliminate the background and far moving objects (other vehicles)        from the further processing;    -   d) the algorithm should work for the static case and allow an        expansion onto dynamic cases;    -   e) the algorithm should be able to use two sequential images        from the camera.

Condition (e) gives an opportunity to use differential images to find alocation of the object in the image. Direct subtracting does not reallyhelp in the dynamic case because the background changes also. Condition(d) could be satisfied if we had taken into account that the closer anobject, the bigger relative changes of its size in two sequential imagesfrom the camera would have been. This fact can be utilized by a searchof local distances between similar edges in the images. A closer objectpresents a bigger distance between the same (similar) edges in this partof the images.

Hence, the first step of the image segmentation is a discrimination ofedges or contours. The discrimination should highlight edges of objectsand, if possible, hide local variations of the brightness in a picture.As soon as the edges are discriminated in both sequential pictures, itsdifference allows an almost complete elimination of motionless objects(“almost” because the illumination can have some variations between twosequentially collected images), and it puts edges on the same image tofind the distances between same edges or objects.

2.1. An Edge Discrimination Algorithm

To achieve the declared goal of the discrimination, the edgediscrimination algorithm is based on processing of images by columns androws. The columns and rows are analyzed separately. During the analysis,most representative edges are kept at a column or a row.

The following adjustable settings are used by the edge discriminationalgorithm: a threshold and a smoothing length. The use of the thresholdallows a suppression of small brightness drop variations. The smoothinglength defines how many neighboring pixels are used to calculate an edgevalue. The smoothing length, L, is intended to hide local variations ofbrightness in the image and somewhat equalize the significance of smoothand sharp edges. The bigger parameter L the smoother edges will be takeninto account and the less will be the influence of local distortionssuch as a bad pixel.

The values (brightness) of pixels after the edge discrimination arecalculated in this way:

1) Using the pixel values, P_(ij), of the original image, values of thegradients R_(ij) are calculated along the image's rows:

$R_{ij} = {{{\sum\limits_{j - L}^{j}P_{ij}} - {\sum\limits_{j + 1}^{j + L + 1}P_{ij}}}}$

The subscripts i and j denote columns and rows, respectively.

2) In the same manner, the gradients C_(ij) are calculated along thecolumns of the image:

$C_{ij} = {{{\sum\limits_{i - L}^{i}P_{ij}} - {\sum\limits_{i + 1}^{i + L + 1}P_{ij}}}}$

3) Finally, for an image with the discriminated edges, values of pixelsP_(ij) ^(n) are computed as maximums of R and C divided by L to staywithin the range of the pixel values:

$P_{ij}^{n} = \frac{\max\left( {R_{ij}^{n},C_{ij}^{n}} \right)}{L}$

The superscript denotes an image after the edge discrimination.

Two sequential images are processed with the algorithm for obtaining thedifferential image. Pixel values of differential image P^(d) arecomputed simply as absolute values of a difference between therespective values of pixels of two sequentially collected images:P _(ij) ^(d) =|P _(ij) ¹ −P _(ij) ²|

A result of the algorithm's application is shown in FIG. 130. FIG. 130shows two sequential images and a differential one. The sequentialimages are one original and one processed by the edge discriminationalgorithm.

2.2 Object Area Selection

Comparison of different image segmentation (object detection) algorithmsshows that the most appropriate one for the current task is a three-stepprocessing. At the first step, the algorithm finds most likely places ofan object's location, or “kernel points”. At the second step, theobject's areas around the kernel points are searched, and at the laststep, an intersection of the area with the desired object is extracted.The algorithm uses the differential image.

The search for most likely locations of an object and the extraction ofthe object areas are based on a processing of parts of an image. Theimage is covered by relatively small windows that form rows and columnsalong the respective directions of the image. For each window, aparameter is calculated, one which can be named “energy”. The energyshows how big is the common value of the edges (pixels) inside thewindow in the differential image. Thus, the set of the window's energiescan be treated as a matrix. For the static case of the task, which isconsidered here, a window energy E can be calculated simply as a sum ofpixel values inside the window W:

$\begin{matrix}{{E_{kl} = {\sum\limits_{i}{\sum\limits_{j}{P_{ij}\mspace{31mu}{\forall i}}}}},{j \Subset W_{kl}}} & (1)\end{matrix}$

Indexes k and l define a window in the image, the indexes i and j areindividual pixels in the differential image that fall inside the window.

When we apply this to the dynamic cases discussed in the introduction,the energy will be calculated as a common value of the distances betweenthe edges in the window. The distances are calculated along the columnsand rows.

Together with the size of the windows, the following adjustable settingsare used to find the object location and area: an overlap factor and athreshold value of energy. The overlap factor belongs to the range [0,1)where “0” means that the windows are placed exactly against each other(not overlapped). The use of the factor is intended to prevent a lack ofinformation at the windows boundaries. The threshold value of energy,T_(E), is used to select kernel points. The value is computed as:

$T_{E} = {E_{av} + \frac{E_{\max} - E_{av}}{\alpha}}$

where α is a free parameter, which is equal to 2 in the currentresearch, E_(av) and E_(max) are an average and a maximum energy overthe windows, respectively:

${{E_{av} = {\sum\limits_{k = 1}^{K}{\sum\limits_{l = 1}^{L}{E_{kl}/\left( {K \cdot L} \right)}}}};}\mspace{25mu}$$E_{\max} = {\max\limits_{k,l}\left( E_{kl} \right)}$

The kernel points are defined as windows for which this holds:T_(E)<E_(kl)

Areas of objects are constructed using an energy matrix. First, an areais defined by top-left (k₁,l₁) and bottom-right (k₂,l₂) indexes of theenergy matrix. The area search algorithm is iterative and starts from akernel point (k,l):k₁=k₂=k; l₁=l₂=l;

The algorithm sequentially adds rows and columns to the object areacounter-clockwise. A row or a column will be added to the area if theaverage energy of the addition is greater than E_(av):

$k_{2}^{\prime} = \left\{ \begin{matrix}{k_{2} + 1} & {\left. {{{if}\mspace{14mu} E_{av}} < \left( {\sum\limits_{k_{1}}^{k_{2}}{E_{kl}/\left( {k_{2} - k_{1}} \right)}} \right)} \middle| l \right. = l_{2}} \\k_{2} & {otherwise}\end{matrix} \right.$

And so on for each index, but indexes k₁ and l₁ decrease. The algorithmstops when for a complete contour path no index can be changed.

The area selection technique is based on several heuristics. Since it issupposed that an object of interest is the closest one, it is mostlikely that the object area is a biggest one among all found in thedifferential image. Another heuristic that can be used is based onproportions of objects relatively close to the shooting point. Since thecamera direction and the field of view are fixed, the expected sizes ofan object area depends on a position of the bottom-left corner of thecovering area. It means that the closer an object it is, the greaterarea of the image it occupies, and the bottom-left corner of the objectwill appear closer to the image bottom.

Results of application of the area selection algorithm are shown inFIGS. 131 and 132. All pixels outside of a found object area inn theimages are suppressed. Thus, using the object recognition technology,the images with selected object areas can be used.

The inaccuracy of the image segmentation algorithm becomes apparent in afew cases and mostly in the form of capturing extra space by the objectarea There are a few of truck pictures where the inaccuracy appears asan incompletely covered object. Among 1620 setups, there is only onecase when the algorithms lost the object. Such possibility appears whenbig objects on the far traffic lane look similar to the sought objectand the found areas are not overlapped. Examples of an inaccurate imagesegmentations are illustrated by FIG. 133.

3. Object Encoding

In view of different positions in the image that conform to differentsizes of objects, the feature vector constructed for patternrepresentation has to reflect this fact. One possible way to extractfeatures that contain information about an object's position andrelative sizes is to construct histograms of distances from the image'ssides to the contours of the object. The distances determine thepositions of the objects. The object sizes are determined by aproportion of the distances. Both horizontal and vertical distances tothe contours from the image sides are informative.

A differential image with a selected object area is used at the currentphase of the investigations. To construct histograms, they used abinarization of edges inn the differential image:

$b_{ij} = \left\{ \begin{matrix}1 & {{{if}\mspace{14mu} T} < P_{ij}} \\0 & {otherwise}\end{matrix} \right.$

Here b_(ij) is a pixel value of a binary image, which corresponds to thedifferential one. Examples of the obtained binary images for cars andtrucks are shown in FIG. 7.

To keep information about the objects' altitude and relative positionsof the visible objects or their parts, bands are used to producehistograms. In some literature, histograms are used for a whole image,but zoning of the image shows better results for this particular task.

Similarly to sliding windows, the bands are characterized by a width,Bw, and an overlap factor, Bf. In addition, a quantization interval Bqis used to construct the histograms. The mentioned variables can bedifferent for the horizontal and vertical bands of histograms. Numbersof histogram elements, N, show how we use with the picture. Nb and thenumber of intervals—per band, Ni:

${Nb} = \frac{\left( {1 + {Bf}} \right) \cdot H}{Bw}$${Ni} = \frac{W}{Bq}$ N = Nb ⋅ Ni

Here W and H are a width and a height of the image, respectively. Itshould be noted that depending on how the last band ends with respect tothe image, the side, Nb, must be increased or decreased per unit.

Lets define p^(h) as:

$p_{ij}^{h} = \left\{ \begin{matrix}1 & {{{if}\mspace{14mu}\left( {\left( {b_{ij} = 1} \right)\bigcap\left( {b_{i{({j + 1})}} = 0} \right)} \right)}\bigcup\left( {\left( {b_{ij} = 0} \right)\bigcap\left( {b_{i{({j + 1})}} = 1} \right)} \right)} \\0 & {otherwise}\end{matrix} \right.$

Here b_(ij) represent a binary image. This simplest heuristic is used tosuppress straight solid lines of contours along the band because suchlines introduce a noise to the space frequency histograms.

Each row, i, of the band, k, will be added to the value, V^(k), of thehistogram element:

$v_{i}^{k} = {{\sum\limits_{j}{p_{ij}^{h}\mspace{31mu} j}} \in \left( {{\left( {k - 1} \right) \cdot {Nq}},{k \cdot {Nq}}} \right\rbrack}$

Finally, the value of a horizontal histogram element is calculated as:

$V^{k} = {{\sum\limits_{i}{v_{i}^{k}\mspace{20mu} i}} \in \left\lbrack {1,{Bw}} \right\rbrack}$

It is possible to separately suppress the straight solid (or evendashed) lines and lines with small angles, but it requires extra cyclesof image processing and is not necessary now. In addition, it can behelpful to use contour reconstruction algorithms and filters toeliminate noisy contours, but both types of algorithms are timeconsuming and because of sufficiently good results of classificationwith the currently used features (see below), the necessity of usingsuch processing is questionable.

A direct use of the calculated values as a neural network input is notconvenient. First, most of the neural network learning algorithms use afixed range of input values (for example, [0,1]), and second, forrecognition of a contour, we are mostly interested not in the distancesof the contours from the image sides, but in a proportion between thedistances. Thus, to compute the feature vector, we used a normalizedhistogram:

$V^{k} = {{\frac{V^{k}}{\max\limits_{k}\left( V^{k} \right)}k} \in \left\lbrack {1,N} \right\rbrack}$

The vertical histogram is constructed in the same manner but the bandsgo along the columns of the binary image.

4. Classification Results

Experiments with a classification of cars vs. trucks were done using arandom selection of the test patterns from the collected data. For astatistical validity, two sets of experiments were run. First theinitial 1620 shots were divided into ˜90% for the training (1460) and˜10% for the testing (160) sets. For the second series of experiments,the division was ˜80% (1300) and ˜20% (320). No generalized ascensionapproach, such as a “save best” method, was used for the neural networktraining.

The training of networks shows that a simplest neural network paradigm(linear perception) solves the problem. In all experiments, a 100%classification rate was obtained both at the training set and at thetesting one. However, the first sets of experiments (90/10%) requiredthe training depth of about 16,000 vectors (near 10 epochs) whereas thesecond set required to pass through about 20,000 vectors (15 epochs) toreach a 100% classification rate with the training set.

Discussion

The selected preprocessing procedures show a very good separability ofthe classes in the constructed feature space. This is evidenced by auselessness of the generalized ascension methods and by a simplicity ofa network required to do the job.

It should be noted especially that even for the case when thesegmentation algorithm lost an object (a car), the network still gave acorrect result because the captured part of the image is similar to theobject by its appearance.

The developed approach seems to be applicable for dynamic cases as well.To prove this conclusion dynamic data will be collected and processed onthe next phase of project. But, the dynamic cases require somemodification for calculating “energy” (see equation 1) and will havemore noise in the feature codes.

Appendix 3: CFD Aspirated Inflator Engineering Summary Report

Introduction

When firing all protective airbags (when there are more than 6 bags)being filled by a gas generating system inside a car simultaneously,pressure inside the car increases drastically at that moment. It cancause the occupants of the car to be severely injured by an additionalpressurization effect. With increasing total volume of airbags, theproblem of injuring occupants will become evident.

It can be avoided by using air inflators in combination with a gasgenerating system for filling the airbags, even at low aspirationratios. At an aspiration ratio of 4, utilization of inflators willdecrease the required power of gas-generating system by three times.Besides, utilization of high-effective inflators, with aspiration ratiosof 4-6, enable utilization of a compressor unit or compressed-air flaskfor filling bags, at boost pressures less than 20 atmospheres.

FIG. 135 shows the pressure in a compressed-air flask/pressure in anairbag vs. the ratio of the airbag's volume and that of the flask;calculated by the formula

$\frac{P_{0}}{P_{bag}} = {\frac{1}{A^{\kappa}}\left( \frac{V_{bag}}{V_{0}} \right)^{\kappa}}$where A is the aspiration ratio, K is the adiabatic exponent (κ=1.4 forair under normal conditions).

With no inflator, making use of an airbag pumping system based on acompressed-air flask (or another gas) does not comply with safetyrequirements, nor with design specifications. For example, if theairbag's volume is 20 times that of the compressed-air flask, then thepressure inside the flask must be 70 atmospheres. At the same time,utilization of an inflator makes the compressed-air flask-based designcomparable to the gas-generating systems by its efficiency. For example,the aspiration ratio of 4 and the ratio between the airbag's and theflask's volume V_(bag)/V₀=50 will lower the pressure in the flask to 35atmospheres. At an aspiration ratio of 6, the pressure in the flask canbe as low as 20 atmospheres or less (FIG. 135).

Formulation of the Problem

The main problem is to find a proper shape for the plane inflator tominimize the length of the mixing chamber, provide a maximum aspirationratio for air being ejected at the ambient pressure, and ensure anappropriate flow rate into the airbag at a nearly ambient pressurehaving the given pressure of 10 to 40 atmospheres in the pressurizedflask.

Two shapes of plane inflators are basic in this analysis:

-   -   one with the high-pressure nozzles placed on the central body of        the inflator (this is an asymmetric configuration—the        high-pressure nozzles are asymmetric with respect to the mixing        chamber);    -   one with the high-pressure nozzles placed on the exterior side        of the inflator (the inflator has no central body). This is a        symmetric configuration—the high-pressure nozzles are symmetric        with respect to the mixing chamber.        Numerical Simulation

There is a well-known problem of finding steady-state characteristicspossessed by a plane or axially symmetrical inflator of a simplegeometry, with either a compressible or incompressible fluid medium. Thesolution to this problem can be obtained by a variety of methods,usually one-dimensional and steady-state ones, which make use of gasdynamic functions. Though, those techniques hardly answer the purpose ofdetermining the shape and minimum size of an inflator that shouldprovide a given flow rate at its output in the pulse jet mode with givendynamical parameters of both the ejecting and the ejected gas. Theproblem is yet more complicated because the time in which the high-speedejecting flow is formed after the high-pressure valve fires and the timein which the ejected gas gains its speed are both comparable with thetime needed to fill the airbag. The reason for this is an intensivevortex-type flow in the mixing chamber which is formed as the shockwavegoes out of the high-speed nozzle and then is re-reflected. In thisregard, one has to analyze a model of such complexity, at the least, asan unsteady-state non-viscous two-dimensional flow of gas (acompressible medium) in an area of a complicated shape. As the viscositydefines both the structure/dimensions of eddies in the flow and the timeof arrival at a steady state, one has to take the viscosity intoaccount, too.

This problem will be governed by the following system of unsteady-statetwo-dimensional equations describing a compressible viscousmedium—Navier-Stokes equation, continuity equations, an energyconservation law represented by a heat conduction equation, and a stateequation:

${{\frac{\partial\left( {\rho\; V_{x}} \right)}{\partial t} + \frac{\partial\left( {\rho\; V_{x}^{2}} \right)}{\partial x} + \frac{\partial\left( {\rho\; V_{x}V_{y}} \right)}{\partial y}} = {{- \frac{\partial P}{\partial x}} + \frac{\partial\tau_{xx}}{\partial x} + \frac{\partial\tau_{xy}}{\partial y}}};$${{\frac{\partial\left( {\rho\; V_{y}} \right)}{\partial t} + \frac{\partial\left( {V_{x}V_{y}} \right)}{\partial x} + \frac{\partial\left( {\rho\; V_{y}^{2}} \right)}{\partial y}} = {{- \frac{\partial P}{\partial y}} + \frac{\partial\tau_{xy}}{\partial x} + \frac{\partial\tau_{yy}}{\partial y}}};$${{\frac{\partial\rho}{\partial t} + \frac{\partial\left( {\rho\; V_{x}} \right)}{\partial x} + \frac{\partial\left( {\rho\; V_{y}} \right)}{\partial y}} = 0};$${T\;{\rho\left( {\frac{\partial H}{\partial t} + {V_{x}\frac{\partial H}{\partial x}} + {V_{y}\frac{\partial H}{\partial y}}} \right)}} = \begin{matrix}{{\frac{\partial}{\partial x}\left( {\kappa\frac{\partial T}{\partial x}} \right)} + {\frac{\partial}{\partial y}\left( {\kappa\frac{\partial T}{\partial y}} \right)} +} \\{{\Phi + {{\zeta div}\left( \overset{\rightarrow}{V} \right)}};}\end{matrix}$ P = ρ RTwhere V_(x)V_(y) are components of the velocity vector, P is thepressure, ρ is the density, H is the entropy, μ, ζ are dynamic viscositycoefficients, κ is the thermal conductivity, T is the temperature, R isthe gas constant, Φ is a dissipative function, τ_(ij) are viscousstresses:

${\tau_{xx} = {{2\mu\frac{\partial V_{x}}{\partial x}} - {\left( {{\frac{2}{3}\mu} - \zeta} \right){div}\;\overset{\rightarrow}{V}}}};{\tau_{yy} = {{2\mu\frac{\partial V_{y}}{\partial y}} - {\left( {{\frac{2}{3}\mu} - \zeta} \right){div}\;\overset{\rightarrow}{V}}}};$${\tau_{xy} = {\mu\left( {\frac{\partial V_{x}}{\partial x} + \frac{\partial V_{y}}{\partial y}} \right)}};{{{div}\;\overset{\rightarrow}{V}} = {{\frac{\partial V_{x}}{\partial x} + {\frac{\partial V_{y}}{\partial y}.\Phi}} = {2{\mu\left\lbrack {\left( \frac{\partial V_{x}}{\partial x} \right)^{2} + \left( \frac{\partial V_{y}}{\partial y} \right)^{2} + \left( {\frac{\partial V_{y}}{\partial x} + \frac{\partial V_{x}}{\partial y}} \right)^{2} - {\frac{2}{3}\left( {{div}\;\overset{\rightarrow}{V}} \right)^{2}}} \right\rbrack}}}};$

The medium is air simulated by the Clapeyron equation with the adiabaticexponent of 1.4. The coefficient of dynamic viscosity and thermalconductivity of the air are assumed to vary with temperature.

Boundary conditions on the walls are: adiabatic conditions, and adhesionof the flow. A static pressure is specified at the input (for both theejecting and the ejected flows) and at the output. Initial conditions:the gas in the inflator is still, the static pressure is equal to theambient pressure.

Results

First stage was calculations of unsteady-state dynamic parameters of gasflows in test problems by the ANSYS software. It has proved quitecredible if an optimum meshing is selected and thus, calculated dynamicparameters of gas flows in the inflators are reliable to some reasonableextent.

Generally, the calculated results confirm the known facts that asupersonic ejecting jet directed along the inflator's axis in asimple-shape area mixes poorly with the low-pressure flow being ejected,and the mixing chamber's length is more than 10-15 its width. Thecalculation seems to determine the shockwave passing time and itsmagnitude pretty accurately, after the high-pressure valve fires. Otherphenomena calculated well enough include the shockwave's reflection,emergence of long-lasting oscillations of the pressure and velocity,time of arrival at the steady state.

Dynamic parameters of the gas inside the inflator were estimated on thebasis of the energy, mass and momentum conservation laws. Thisestimation enabled us to determine ultimate values of the average flowrate in the inflator needed to provide the given consumption after 3040is. Numerical results obtained were the basis for requirements to theinflator's geometry and the high pressure magnitude needed to achievethe required flow rate at a given pressure and with the maximumaspiration ratio.

The principal idea is to minimize the length of the mixing chamber dueto the ejection effect by using a high-speed wall jet directed at alarge angle to the inflator's axis which will make use of Coanda'seffect and create longitudinal perturbations to intensify the mixingbetween flows running at different speeds.

The Central-Body Inflator

Typical shape of the first type of inflator is shown in FIG. 136 inwhich the nozzles are placed asymmetrically with respect to the mixingchamber of the variable thickness.

The computation of dynamic parameters of the flow and the flowrate/consumption in the inflator allow the influence of geometricalproperties of the inflator to be determined at a given pressure of theejecting flow.

Key points in the operation of the pulse inflator that ejects thefree-flow air from inside the car are: a high-speed (pressurizing)nozzle; the geometry of its joint with the mixing chamber; the ratio ofthe thickness of the nozzle's outlet to that of the mixing chamber; thelength of the mixing chamber; the static pressure at the outlet from theinflator.

The geometry and other properties of the nozzle must be such that thefully formed jet does not separate from the wall while being looseenough (as the supersonic jet turns, expansion waves emerge at itsoutside). This will ensure its quick mixing with the flow being ejected.FIG. 137 presents a calculated result for a characteristic velocityfield in the inflator after the steady state is achieved (10milliseconds). FIG. 137 shows a non-uniformity of the velocity fieldwhich cannot be eliminated even in a pretty long chamber (L/h=8).

After the nozzle and the way it is jointed to the mixing chamber havebeen chosen, the mixing chamber, the confuser and diffuser parts of theinflator are analyzed and simulated. This is a long and laboriousprocess, but the result of it is a great deal of physical informationregarding the time history of the flow. This information is of greathelp to develop mechanisms for controlling the flow's structure.

The results of the calculation enable construction of a theoreticaldrawing of the inflator conforming to certain requirements (such asdimensions, flow rate, aspiration ratio). The theoretical drawing wasthe basis for a production drawing of the inflator. The calculatedresults were validated experimentally with the inflator mockups made inconformance with the theoretical drawings.

FIG. 138 shows drawings of the plane inflators, batches A1-A5, and somemodifications tested.

Slots for the injected high-speed jet are located in the central body.The notations in FIG. 137 correspond to test batches as follow: I—batchA1; II—batch A2-1; III—batch A2-2; IV—batch A4, A5; V—batch A2-2modified (high-speed jet is controlled by creating longitudinal vorticalstructures over the coupling section between the slot and mixingchamber); A—the slot thickness (δ_(slot)); Z—minimum section size;B—outlet size.

FIG. 139 shows the appearance of batch A1. Width of the inflator isL=150 mm, outlet B=22.4 m.

To perform experimental investigations of inflator samples, theexperimental setup was assembled which allows for creating pulsehigh-speed jet with controllable duration of work cycle of t≈120-350 msand measuring volumetric rate for a fixed time period. Work pressure forcreating the jet can vary in the range P_(H)=800−3500 kPa.

To record boosting time of the inflator, fast-response semiconductorsensors were mounted before the slot (sensors MPX5 of Motorola andML500PS2PC of Honeywell, operating pressure ranges up to 50 kPa, 1000kPa and 3500 kPa)

The aim of tests was to determine volumetric rate of air through theinflator at open (Q_(P)=Q_(S)+Q_(H)) and closed (Q_(H)) canal for airfrom inside a vehicle. It allows for calculating the aspiration ratio asa function of pressure in the discharge chamber, K_(asp)=Q_(P)/Q_(H).

Also measured was static pressure along the upper wall of the inflator.For this, catchments were made at following locations (FIG. 136): a) atthe wall of the drawoff confusor (R), b) at the exit of high-speed jet(G), c) in the diffuser of the mixing chamber (L). Sensors MPX5050DPwere used to measure pressure. The appearance of the inflator A5assembled with a bag, electromagnetic air-valves and sensors is shown inFIG. 140.

Numerical calculations for different modifications of inflator were thebasis to determine the shape which provide minimum losses in theinflator, at given size of inflator. Typical calculated flow pattern inthe A1-1 inflator is presented in FIG. 137. FIGS. 141A and 141B showpressure and velocity profiles across the mixing chamber in the locationafter the slot exit where high-speed jet mixes with free air flow frominside a vehicle. FIG. 141C presents calculated pressure distributionalong the wall of the inflator.

FIG. 142 shows pressure (negative value) measured at the locations L,G,R(FIG. 136) during the period when high-pressure valve is open.

FIG. 143 presents calculation results and measured data for volumetricrate, and FIG. 144 shows the aspiration ratio, in dependence on boostpressure in the inflator A1-1 (z=4.5 mm; δ_(slot)=0.075 mm).

Measured pressure inside the inflator (FIG. 142), at boost pressure ofup to 20 atmospheres, validates qualitatively and, the most important,quantitatively calculation results (FIG. 141C).

So, results of numerical analysis and tests proved to be complementaryand are in a good agreement, in given range of driving parameters.

When boost pressure grows, volumetric rate increases. However, atparticular pressure value (P_(av)≈22 atm, FIG. 143), the inflator locksup partly. It happened because the high-speed jet, after it exits fromthe slot A, separates from the wall and “hits” the opposite wall (seelocation G, case C in FIG. 136). In locations G and R pressure becomespositive, as can be seen from the sensor blockage. In this case,aspiration ratio drops (FIG. 144). Numerical calculations at such valuesof boost pressure presented high oscillations of pressure and velocity.In the absence of measured data, it had been related to numericalinstability.

Modification of the high-pressure slot shape and size allows forincreasing the threshold boost pressure and correspondingly increasingtotal air-flow rate. The aspiration ratio also increases.

Two ways were analyzed to control flow in the mixing zone of inflator.

The first way was to change the size and shape of the mixing chamber.Increasing width (Z) in the beginning of the chamber (case II (batchA2-2, z=9 mm) and case III (batch A2-3, z=7 mm) in FIG. 138) has lead toincreasing flow rate and aspiration ratio (FIGS. 145 and 146)

The second was a modification of coupling between the mixing chamber andhigh-speed slot. More effective mixing was attained with the modifiedinflator A2-4 (case V in FIG. 138), in comparison with initial A2-3(case III in FIG. 138). Correspondingly, the aspiration ratio is higher(FIG. 147).

Based on the gained experience, our next step was design of the planeinflator of batch A5 (L=200 mm) (FIG. 140), analogical in generalassembling to A1. Tested modification of this batch are shown in FIG.148.

Test results for A5 are presented in FIGS. 149 and 150. This batchproduced higher air flow rates.

Based on these results, we conclude that the central-body inflators arecapable of ensuring that a protection airbag containing 30 to 60 litersis filled in 40 μs with the aspiration ratio 4 to 5 at the pressure 30atmospheres. The total consumption of 33 liters in 40 μs has beenconfirmed experimentally with the inflator #2.

The No-Central-Body Inflator

A second object of the research was a no-central-body inflator where thehigh-pressure nozzles were installed on the outside of the inflator(FIG. 151). The key difference from the previous case is that thenozzles are symmetric with respect to the mixing chamber, so thesupersonic jets affect each other. In this inflator, friction losses areless intensive because the device does not have two surfaces, therelative length of the mixing chamber is less, but the loss due to largeeddies are somewhat larger (FIG. 152).

The appearance of the inflator A6 assembled with a bag andelectromagnetic air-valves is shown in FIG. 153.

Measured data for modifications A6-1 (2z=50 mm) and A6-2 (2z=34 mm)(index 2) are presented in FIGS. 154 and 155.

In should be noted, that minor changes in its shape at the high-speedjet exit affect essentially the integral aerodynamic characteristics andcan worsen its performance (batch A6-1, batch A6-2, index 1).

CONCLUSIONS

FIGS. 156 and 157 present calculation results of total flow rate andaspiration ratio in different inflators vs. high static pressure in theflask that generates the high-speed jet.

In FIG. 158, experimentally measured flow rate are shown, for differentmodifications of inflators from batches A0-A6.

So, the following can be stated:

1. The performed investigations have validated performance of aninflator in the system filling an airbag in pulse regime when free-flowair from inside a vehicle is aspirated.

2. The performed investigations have revealed the high performance ofinflators with high-speed slot located at the outer walls (theno-central-body inflator), in comparison with the central-body inflator.

3. The investigations allowed for determining the shape of the mixingchamber, slot location and shape, its coupling to the mixing chamber,the value of boost pressure providing the specified volumetric flow intoan airbag for 40 milliseconds.

4. Utilization of vortical controlling the high-speed jet allows forimproving performance of the inflator for more than 30%, by improvingmixing in the mixing chamber and avoiding jet separation at thresholdvalues of boost pressure.

1. A method for inflating an airbag in a vehicle to protect an occupantin the event of a crash involving the vehicle, comprising: arranging aninflator having a propellant in the vehicle; igniting the propellantafter determination of a crash involving the vehicle to generate gastherefrom; directing the gas into an airbag to cause the airbag todeploy; forming at least one variable gas flow port to enable a variableflow of gas into the airbag during deployment, the at least one variablegas flow port being formed in a flow path of the generated gas between alocation at which the gas is generated and the airbag or being formed ata location between a location where the inflator is attached to asupporting base and the airbag; and controlling pressure in the airbagbased on the occupant by varying the at least one variable gas flow portand thereby providing for a controlled pressure in the airbag.
 2. Themethod of claim 1, wherein the variation in the flow of gas into theairbag is obtained by varying a flow of aspirating gas into a mixingchamber in which the aspirating gas mixes with gas generated from thepropellant, the mixing chamber being located between the location atwhich the gas is generated and the airbag.
 3. The method of claim 2,wherein the inflator has at least one variable passage through which thegas flows in a path toward the airbag, the cross-sectional area of theat least one passage being controlled based on the pressure in themixing chamber.
 4. The method of claim 1, further comprising arrangingthe inflator and the airbag in a housing having a cover exposed to apassenger compartment of the vehicle, the pressure in the airbag beingcontrolled during deployment when the cover is interposed between theairbag and the occupant based on the occupant's position relative to thecover.
 5. The method of claim 4, wherein pressure in the airbag iscontrolled to prevent injury to the occupant when the occupant isleaning on the cover and preventing deployment of the airbag.
 6. Themethod of claim 4, wherein the step of controlling pressure in theairbag comprises opening ports when the occupant is leaning on the coverand preventing deployment of the airbag such that gas generated from thepropellant flows out through the ports and not into the airbag when theoccupant is leaning on the cover and preventing deployment of theairbag.
 7. The method of claim 1, wherein the at least one variable gasflow port comprises a plurality of variable gas flow ports, the size ofthe ports being dependent on pressure exerted by the occupant againstthe airbag.
 8. The method of claim 1, wherein pressure in the airbag iscontrolled based on the occupant's position relative to the airbag. 9.The method of claim 1, wherein the at least one variable gas flow portis formed in a flow path of the generated gas between a location atwhich the gas is generated and the airbag.
 10. The method of claim 1,wherein the at least one variable gas flow port is formed at a locationbetween a location where the inflator is attached to a supporting baseand the airbag.
 11. A method for controlling combustion of a propellantwhich produces gas when burning, the gas being used to inflate an airbagon a vehicle, comprising: housing the propellant in a combustion chamberon the vehicle; forming a mixing chamber in which the gas generated uponcombustion of the propellant mixes with a flow of aspirating gas withthe mixed flow being directed into the airbag; providing at least oneexit conduit from the combustion chamber through which gas generatedupon combustion of the propellant flows into the mixing chamber; andadjusting the cross-sectional area of the at least one exit conduitduring combustion of the propellant to thereby continuously control thepressure in the combustion chamber and thus the rate of combustion ofthe propellant.
 12. The method of claim 11, wherein the combustionchamber is defined by a gas generator, further comprising mounting thegas generator to a base to thereby define a nozzle between the gasgenerator and the base which constitutes an exit conduit.
 13. The methodof claim 12, wherein the cross-sectional area of the nozzle is adjustedby mounting the gas generator to the base via an elastic or flexiblesupporting structure which holds the gas generator against the base. 14.The method of claim 13, wherein the gas generator moves apart from thebase to thereby increase the cross-sectional area of the nozzle whenpressure in the combustion chamber exerts a force greater than the forceprovided by the supporting structure.
 15. The method of claim 12,further comprising maintaining a minimum cross-sectional area of thenozzle by arranging supports between a surface of the gas generatorfacing the base and the base.
 16. The method of claim 12, wherein thecross-sectional area of the nozzle is adjusted by mounting the gasgenerator to the base via a deformable supporting structure.
 17. Asystem for controlling combustion of a propellant which produces gaswhen burning, the gas being used to inflate an airbag on a vehicle,comprising: a housing; and an inflator including a combustion chamberhaving a propellant which generates gas upon burning, said housingdefining a mixing chamber in which the gas generated upon combustion ofsaid propellant mixes with a flow of aspirating gas with the mixed flowbeing directed into the airbag; said inflator being mounted to saidhousing to define at least part of at least one exit conduit from saidcombustion chamber and through which gas generated from said propellantflows into the mixing chamber and such that said at least one exitconduit is capable of having an adjustable cross-sectional area duringcombustion of said propellant to thereby continuously control thepressure in said combustion chamber and thus the rate of combustion ofsaid propellant.
 18. The system of claim 17, wherein the cross-sectionalarea of said at least one exit conduit is controlled based on thepressure in said combustion chamber.
 19. The system of claim 17, furthercomprising an elastic or flexible supporting structure for mounting saidinflator to said housing and loading said inflator toward said housing,the cross-sectional area of said at least one exit conduit beingadjustable based on pressure differences between a pressure in saidcombustion chamber and a pressure provided by said supporting structure.20. The system of claim 19, further comprising support structurearranged between a surface of said inflator facing said housing and saidhousing for maintaining a minimum cross-sectional area of said at leastone exit conduit.
 21. The system of claim 17, further comprising adeformable supporting structure for mounting said inflator to saidhousing, the cross-sectional area of said at least one exit conduitbeing adjusted upon deformation of said supporting structure.
 22. Thesystem of claim 17, wherein said housing defines at least one variablegas flow port which enables gas flow from an interior of said housing toan exterior of said housing, said at least one gas flow port enablinggas to flow into said mixing chamber defined by said housing and combinewith gas generated from said propellant and flowing through said atleast one exit conduit which then flows out of said housing into theairbag.
 23. The system of claim 22, further comprising a coverreleasably mounted to said housing for covering the airbag, said atleast one gas flow port being defined between said cover and a remainingpart of said housing.
 24. The system of claim 22, wherein thecross-sectional area of said at least one exit conduit is controlledbased on the pressure in said mixing chamber.
 25. An occupant protectionsystem for protecting an occupant in a vehicle in the event of anaccident involving the vehicle, comprising: at least one airbag arrangedto deploy into a passenger compartment of the vehicle; an inflatorsystem for inflating said at least one airbag, said inflator systemcomprising a housing, and an inflator including a combustion chamberhaving a propellant which generates gas upon burning, said housingdefining a mixing chamber in which the gas generated upon burning ofsaid propellant mixes with a flow of aspirating gas with the mixed flowbeing directed into said at least one airbag, said inflator beingmounted to said housing to define at least one exit conduit from saidcombustion chamber and through which gas generated from said propellantflows into said mixing chamber, said at least one exit conduit having anadjustable cross-sectional area; and an initiation device affanged toinitiate burning of said propellant in response to an accident involvingthe vehicle such that upon burning of said propellant, gas is generatedand flows through said at least one exit conduit into said at least oneairbag to inflate said at least one airbag.
 26. The system of claim 25,wherein said housing defines at least one variable gas flow port whichenables gas flow from an interior of said housing to an exterior of saidhousing, said at least one gas flow port enabling gas to flow into saidmixing chamber defined by said housing and combine with gas generatedfrom said propellant and flowing through said at least one exit conduitwhich then flows out of said housing.
 27. The system of claim 26,wherein the cross-sectional area of said at least one exit conduit iscontrolled based on the pressure in said mixing chamber.
 28. The systemof claim 26, wherein said inflator system further comprises a coverreleasably mounted to said housing and covering said at least one airbagprior to inflation of said at least one airbag, said at least one gasflow port being defined between said cover and a remaining part of saidhousing.
 29. The system of claim 25, wherein the cross-sectional area ofsaid at least one exit conduit is controlled based on the pressure insaid combustion chamber.
 30. The system of claim 25, wherein saidinflator system further comprises an elastic or flexible supportingstructure for mounting said inflator to said housing and loading saidinflator toward said housing, the cross-sectional area of said at leastone exit conduit being adjustable based on a pressure difference betweena pressure in said combustion chamber and a pressure provided by saidsupporting structure.
 31. The system of claim 30, wherein said inflatorsystem further comprises support structure arranged between a surface ofsaid inflator facing said housing and said housing for maintaining aminimum cross-sectional area of said at least one exit conduit.
 32. Amethod for inflating an airbag in a vehicle to protect an occupant inthe event of a crash involving the vehicle, comprising: arranging aninflator having a propellant in the vehicle; igniting the propellantafter determination of a crash involving the vehicle to generate gastherefrom; directing the gas into an airbag; controlling pressure in theairbag by varying the flow of gas into the airbag; and arranging theinflator in a housing having a cover exposed to a passenger compartmentof the vehicle, the pressure in the airbag being controlled based on theoccupant's position relative to the cover, the step of controllingpressure in the airbag based on the occupant comprising forming variablegas flow ports, the size of the gas flow ports being dependent onpressure exerted by the occupant against the airbag, each of the gasflow ports being formed in a flow path of the generated gas between alocation at which the gas is generated and the airbag or being formed ata location between a location where the inflator is attached to asupporting base and the airbag.
 33. The method of claim 32, wherein atleast one of the gas flow ports is formed in a flow path of thegenerated gas between a location at which the gas is generated and theairbag.
 34. The method of claim 32, wherein at least one of the gas flowports is formed at a location between a location where the inflator isattached to a supporting base and the airbag.
 35. A method for inflatingan airbag in a vehicle to protect an occupant in the event of a crashinvolving the vehicle, comprising: arranging an inflator having apropellant in the vehicle; igniting the propellant after determinationof a crash involving the vehicle to generate gas therefrom; directingthe gas into an airbag; and controlling pressure in the airbag byvarying the flow of gas into the airbag; the step of controllingpressure in the airbag based on the occupant comprising forming variablegas flow ports, the size of the gas flow ports being dependent onpressure exerted by the occupant against the airbag, each of the gasflow ports being formed in a flow path of the generated gas between alocation at which the gas is generated and the airbag or being formed ata location between a location where the inflator is attached to asupporting base and the airbag.
 36. The method of claim 35, wherein atleast one of the gas flow ports is formed in a flow path of thegenerated gas between a location at which the gas is generated and theairbag.
 37. The method of claim 35, wherein at least one of the gas flowports is formed at a location between a location where the inflator isattached to a supporting base and the airbag.
 38. A method forcontrolling combustion of a propellant which produces gas when burning,the gas being used to inflate an airbag on a vehicle, comprising:housing the propellant in a chamber on the vehicle, the chamber beingdefined by a gas generator; mounting the gas generator to a base tothereby define a nozzle between the gas generator and the base whichconstitutes an exit conduit; arranging the exit conduit in flowcommunication with the chamber; and adjusting the cross-sectional areaof the exit conduit during combustion of the propellant to therebycontinuously control the pressure in the chamber and thus the rate ofcombustion of the propellant, the cross-sectional area of the nozzlebeing adjusted by mounting the gas generator to the base via an elasticor flexible supporting structure which holds the gas generator againstthe base.
 39. The method of claim 38, wherein the gas generator movesapart from the base to thereby increase the cross-sectional area of thenozzle when pressure in the chamber exerts a force greater than theforce provided by the supporting structure.
 40. A method for controllingcombustion of a propellant which produces gas when burning, the gasbeing used to inflate an airbag on a vehicle, comprising: housing thepropellant in a chamber on the vehicle, the chamber being defined by agas generator; mounting the gas generator to a base to thereby define anozzle between the gas generator and the base which constitutes an exitconduit; arranging the exit conduit in flow communication with thechamber; adjusting the cross-sectional area of the exit conduit duringcombustion of the propellant to thereby continuously control thepressure in the chamber and thus the rate of combustion of thepropellant; and maintaining a minimum cross-sectional area of the nozzleby arranging supports between a surface of the gas generator facing thebase and the base.
 41. A method for controlling combustion of apropellant which produces gas when burning, the gas being used toinflate an airbag on a vehicle, comprising: housing the propellant in achamber on the vehicle, the chamber being defined by a gas generator;mounting the gas generator to a base to thereby define a nozzle betweenthe gas generator and the base which constitutes an exit conduit;arranging the exit conduit in flow communication with the chamber; andadjusting the cross-sectional area of the exit conduit during combustionof the propellant to thereby continuously control the pressure in thechamber and thus the rate of combustion of the propellant, thecross-sectional area of the nozzle being adjusted by mounting the gasgenerator to the base via a deformable supporting structure.
 42. Asystem for controlling combustion of a propellant which produces gaswhen burning, the gas being used to inflate an airbag on a vehicle,comprising: a housing; an inflator including a chamber having apropellant which generates gas upon burning, said inflator being mountedto said housing to define at least part of at least one exit conduittherebetween in flow communication with said chamber and through whichgas generated from said propellant flows into the airbag and such thatsaid at least one exit conduit is capable of having an adjustablecross-sectional area during combustion of said propellant to therebycontinuously control the pressure in said chamber and thus the rate ofcombustion of said propellant; and an elastic or flexible supportingstructure for mounting said inflator to said housing and loading saidinflator toward said housing, the cross-sectional area of said at leastone exit conduit being adjustable based on pressure differences betweena pressure in said chamber and a pressure provided by said supportingstructure.
 43. The system of claim 42, further comprising supportstructure arranged between a surface of said inflator facing saidhousing and said housing for maintaining a minimum cross-sectional areaof said at least one exit conduit.
 44. A system for controllingcombustion of a propellant which produces gas when burning, the gasbeing used to inflate an airbag on a vehicle, comprising: a housing; aninflator including a chamber having a propellant which generates gasupon burning, said inflator being mounted to said housing to define atleast part of at least one exit conduit therebetween in flowcommunication with said chamber and through which gas generated fromsaid propellant flows into the airbag and such that said at least oneexit conduit is capable of having an adjustable cross-sectional areaduring combustion of said propellant to thereby continuously control thepressure in said chamber and thus the rate of combustion of saidpropellant; and a deformable supporting structure for mounting saidinflator to said housing, the cross-sectional area of said at least oneexit conduit being adjusted upon deformation of said supportingstructure.
 45. An occupant protection system for protecting an occupantin a vehicle in the event of an accident involving the vehicle,comprising: at least one airbag arranged to deploy into a passengercompartment of the vehicle; an inflator system for inflating said atleast one airbag, said inflator system comprising a housing, and aninflator including a chamber having a propellant which generates gasupon burning, said inflator being mounted to said housing to define atleast one exit conduit in flow communication with said chamber andthrough which gas generated from said propellant flows to inflate saidat least one airbag, said at least one exit conduit having an adjustablecross-sectional area; and an initiation device arranged to initiateburning of said propellant in response to an accident involving thevehicle such that upon burning of said propellant, gas is generated andflows through said at least one exit conduit into said at least oneairbag to inflate said at least one airbag, said inflator system furthercomprising an elastic or flexible supporting structure for mounting saidinflator to said housing and loading said inflator toward said housing,the cross-sectional area of said at least one exit conduit beingadjustable based on a pressure difference between a pressure in saidchamber and a pressure provided by said supporting structure.
 46. Thesystem of claim 45, wherein said inflator system further comprisessupport structure arranged between a surface of said inflator facingsaid housing and said housing for maintaining a minimum cross-sectionalarea of said at least one exit conduit.
 47. A method for inflating anairbag in a vehicle to protect an occupant in the event of a crashinvolving the vehicle, comprising: arranging an inflator having apropellant in the vehicle; igniting the propellant after determinationof a crash involving the vehicle to generate gas therefrom; directingthe gas into an airbag to cause the airbag to deploy; arranging theinflator and the airbag in a housing having a cover exposed to apassenger compartment of the vehicle; forming at least one variable gasflow port to enable a variable flow of gas into the airbag duringdeployment; and controlling pressure in the airbag by varying the atleast one variable gas flow port based on the occupant and therebyproviding for a variable pressure in the airbag, the pressure in theairbag being controlled during deployment when the cover is interposedbetween the airbag and the occupant based on the occupant's positionrelative to the cover, the step of controlling pressure in the airbagbased on the occupant comprises opening exhaust ports when the occupantis leaning on the cover and preventing deployment of the airbag suchthat gas generated from the propellant flows out through the exhaustports and not into the airbag when the occupant is leaning on the coverand preventing deployment of the airbag.
 48. A method for controllingcombustion of a propellant which produces gas when burning, the gasbeing used to inflate an airbag on a vehicle, comprising: housing thepropellant in a first combustion chamber on the vehicle; igniting thepropellant to cause combustion of the propellant and generation of gasfrom the propellant; forming a second chamber external to the firstchamber; providing at least one exit conduit from the first chamberthrough which all of gas generated upon combustion of the propellantflows into the second chamber; and adjusting the cross-sectional area ofthe at least one exit conduit during combustion of the propellant tothereby vary the flow of gas generated upon combustion of the propellantinto the second chamber, the variation enabling continuous control ofthe pressure in the combustion chamber and thus the rate of combustionof the propellant.